query: medical_specialty sexually transmitted infection
supports: Infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to these organisms and the toxins they produce. Infectious disease, also known as transmissible disease or communicable disease, is illness resulting from an infection.
  Infections are caused by infectious agents including viruses, viroids, prions, bacteria, nematodes such as parasitic roundworms and pinworms, arthropods such as ticks, mites, fleas, and lice, fungi such as ringworm, and other macroparasites such as tapeworms and other helminths. Vaginal discharge is a mixture of liquid, cells, and bacteria that lubricates and protects the vagina. This mixture is constantly produced by the cells of the vagina and cervix and it exits the body through the vaginal opening. The composition, amount, and quality of discharge varies between individuals as well as through the various stages of sexual and reproductive development. Normal vaginal discharge may have a thinner, watery consistency or a thick, sticky consistency, and may be clear or white in color. Normal vaginal discharge may be large in volume but typically does not have a strong odor, nor is it typically associated with itching or pain. While most discharge represents normal functioning of the body, some changes in discharge can reflect infection or other pathological processes. Infections that may cause changes in vaginal discharge include vaginal yeast infections, bacterial vaginosis, and sexually transmitted infections. The characteristics of abnormal vaginal discharge vary depending on the cause, but common features include a change in color, a foul odor, and associated symptoms such as itching, burning, pelvic pain, or pain during sexual intercourse. Caesarean section, also known as C-section, is the use of surgery to deliver one or more babies. A Caesarean section is often performed when a vaginal delivery would put the baby or mother at risk. This may include obstructed labour, twin pregnancy, high blood pressure in the mother, breech birth, problems with the placenta, umbilical cord or shape of the pelvis, and previous C-section. A trial of vaginal birth in some of these situations, including after C-section, may be possible. Some C-sections are also performed upon request. The World Health Organization recommends that they should be done based on medical need and in many cases they are lifesaving for the mother and baby.
  A C-section typically takes 45 minutes to an hour. It may be done with a spinal block such that the woman is awake or under general anesthesia. A urinary catheter is used to drain the bladder and the skin of the abdomen is then cleaned with an antiseptic. An incision of about 15 cm (6 inches) is then typically made through the mother's lower abdomen. The uterus is then opened with a second incision and the baby delivered. The incisions are then stitched closed. A woman can typically begin breastfeeding as soon as she is awake and out of the operating room. Often a number of days are required in hospital to recover sufficiently to return home.
  C-sections result in a small overall increase in poor outcomes in low risk pregnancies. They also typically take longer to heal from, about six weeks, than vaginal birth. The increased risks include breathing problems in the baby and amniotic fluid embolism and postpartum bleeding in the mother. Established guidelines recommend that caesarean sections not be used before 39 weeks of pregnancy without a medical reason. The method of delivery does not appear to have an effect on subsequent sexual function.
  In 2012, about 23 million C-sections were done globally. The international healthcare community has previously considered the rate of 10% and 15% to be ideal for caesarean sections. Some evidence finds a higher rate of 19% may result in better outcomes. More than 45 countries globally have C-section rates less than 7.5% while more than 50 have rates greater than 27%. There are efforts to both improve access to and reduce the use of C-section. In the United States about 33% of deliveries are by C-section. The surgery has been performed at least as far back as 715 BC following the death of the mother with the occasional baby surviving. Descriptions of mothers surviving date back to the 1500s. With the introduction of antiseptics and anesthetics in the 1800s survival of both the mother and baby became common. Pelvic inflammatory disease or pelvic inflammatory disorder (PID) is an infection of the upper part of the female reproductive system namely the uterus, fallopian tubes, and ovaries, and inside of the pelvis. Often there may be no symptoms. Signs and symptoms, when present may include lower abdominal pain, vaginal discharge, fever, burning with urination, pain with sex, or irregular menstruation. Untreated PID can result in long term complications including infertility, ectopic pregnancy, chronic pelvic pain, and cancer.
  The disease is caused by bacteria that spread from the vagina and cervix. Infections by "Neisseria gonorrhoeae" or "Chlamydia trachomatis" are present in 75 to 90 percent of cases. Often multiple different bacteria are involved. Without treatment about 10 percent of those with a chlamydial infection and 40 percent of those with a gonorrhea infection will develop PID. Risk factors are similar to those of sexually transmitted infections generally and include a high number of sexual partners and drug use. Vaginal douching may also increase the risk. The diagnosis is typically based on the presenting signs and symptoms. It is recommended that the disease be considered in all women of childbearing age who have lower abdominal pain. A definitive diagnosis of PID is made by finding pus involving the fallopian tubes during surgery. Ultrasound may also be useful in diagnosis.
  Efforts to prevent the disease include not having sex or having few sexual partners and using condoms. Screening women at risk for chlamydial infection followed by treatment decreases the risk of PID. If the diagnosis is suspected, treatment is typically advised. Treating a woman's sexual partners should also occur. In those with mild or moderate symptoms a single injection of the antibiotic ceftriaxone along with two weeks of doxycycline and possibly metronidazole by mouth is recommended. For those who do not improve after three days or who have severe disease intravenous antibiotics should be used.
  Globally about 106 million cases of chlamydia and 106 million cases of gonorrhea occurred in 2008. The number of cases of PID however, is not clear. It is estimated to affect about 1.5 percent of young women yearly. In the United States PID is estimated to affect about one million people yearly. A type of intrauterine device (IUD) known as the Dalkon shield led to increased rates of PID in the 1970s. Current IUDs are not associated with this problem after the first month. Vaginal yeast infection, also known as candidal vulvovaginitis and vaginal thrush, is excessive growth of yeast in the vagina that results in irritation. The most common symptom is vaginal itching, which may be severe. Other symptoms include burning with urination, white and thick vaginal discharge that typically does not smell bad, pain with sex, and redness around the vagina. Symptoms often worsen just before a woman's period.
  Vaginal yeast infections are due to excessive growth of "Candida". These yeast are normally present in the vagina in small numbers. It is not classified as a sexually transmitted infection; however, it may occur more often in those who are frequently sexually active. Risk factors include taking antibiotics, pregnancy, diabetes, and HIV/AIDS. Eating a diet high in simple sugar may also play a role. Tight clothing, type of underwear, and personal hygiene do not appear to be factors. Diagnosis is by testing a sample of vaginal discharge. As symptoms are similar to that of the sexually transmitted infections, chlamydia and gonorrhea, testing may be recommended.
  Despite the lack of evidence, wearing cotton underwear and loose fitting clothing is often recommended as a preventative measure. Avoiding douching and scented hygiene products is also recommended. Treatment is with an antifungal medication. This may be either as a creams such as clotrimazole or with oral medications such as fluconazole. Probiotics have not been found to be useful for active infections.
  About 75% of women have at least one vaginal yeast infection at some point in their lives while nearly half have at least two. About 5% have more than three infections in a single year. It is the second most common cause of vaginal inflammation after bacterial vaginosis. Neisseria gonorrhoeae, also known as gonococci (plural), or gonococcus (singular), is a species of Gram-negative coffee bean-shaped diplococci bacteria responsible for the sexually transmitted infection gonorrhea. Human immunodeficiency virus infection and acquired immune deficiency syndrome (HIV/AIDS) is a spectrum of conditions caused by infection with the human immunodeficiency virus (HIV). Following initial infection, a person may not notice any symptoms or may experience a brief period of influenza-like illness. Typically, this is followed by a prolonged period with no symptoms. As the infection progresses, it interferes more with the immune system, increasing the risk of common infections like tuberculosis, as well as other opportunistic infections, and tumors that rarely affect people who have working immune systems. These late symptoms of infection are referred to as AIDS. This stage is often also associated with weight loss.
  HIV is spread primarily by unprotected sex (including anal and oral sex), contaminated blood transfusions, hypodermic needles, and from mother to child during pregnancy, delivery, or breastfeeding. Some bodily fluids, such as saliva and tears, do not transmit HIV. Methods of prevention include safe sex, needle exchange programs, treating those who are infected, and male circumcision. Disease in a baby can often be prevented by giving both the mother and child antiretroviral medication. There is no cure or vaccine; however, antiretroviral treatment can slow the course of the disease and may lead to a near-normal life expectancy. Treatment is recommended as soon as the diagnosis is made. Without treatment, the average survival time after infection is 11 years.
  In 2015 about 36.7 million people were living with HIV and it resulted in 1.1 million deaths. Most of those infected live in sub-Saharan Africa. Between its discovery and 2014 AIDS has caused an estimated 39 million deaths worldwide. HIV/AIDS is considered a pandemica disease outbreak which is present over a large area and is actively spreading. HIV is believed to have originated in west-central Africa during the late 19th or early 20th century. AIDS was first recognized by the United States Centers for Disease Control and Prevention (CDC) in 1981 and its causeHIV infectionwas identified in the early part of the decade.
  HIV/AIDS has had a great impact on society, both as an illness and as a source of discrimination. The disease also has large economic impacts. There are many misconceptions about HIV/AIDS such as the belief that it can be transmitted by casual non-sexual contact. The disease has become subject to many controversies involving religion including the Catholic Church's decision not to support condom use as prevention. It has attracted international medical and political attention as well as large-scale funding since it was identified in the 1980s. Hepatitis C is an infectious disease caused by the hepatitis C virus (HCV) that primarily affects the liver. During the initial infection people often have mild or no symptoms. Occasionally a fever, dark urine, abdominal pain, and yellow tinged skin occurs. The virus persists in the liver in about 75% to 85% of those initially infected. Early on chronic infection typically has no symptoms. Over many years however, it often leads to liver disease and occasionally cirrhosis. In some cases, those with cirrhosis will develop complications such as liver failure, liver cancer, or esophageal and gastric varices.
  HCV is spread primarily by blood-to-blood contact associated with intravenous drug use, poorly sterilized medical equipment, needlestick injuries in healthcare, and transfusions. Using blood screening, the risk from a transfusion is less than one per two million. It may also be spread from an infected mother to her baby during birth. It is not spread by superficial contact. It is one of five known hepatitis viruses: A, B, C, D, and E. Diagnosis is by blood testing to look for either antibodies to the virus or its RNA. Testing is recommended in all people who are at risk.
  There is no vaccine against hepatitis C. Prevention includes harm reduction efforts among people who use intravenous drugs and testing donated blood. Chronic infection can be cured about 90% of the time with treatments that include the medications sofosbuvir or simeprevir. Previous to this a combination of peginterferon and ribavirin was used which had a cure rate around 50% and greater side effects. Getting access to the newer treatments however can be expensive. Those who develop cirrhosis or liver cancer may require a liver transplant. Hepatitis C is the leading reason for liver transplantation, though the virus usually recurs after transplantation.
  An estimated 130200 million people worldwide are infected with hepatitis C. In 2013 about 11 million new cases occurred. It occurs most commonly in Africa and Central and East Asia. About 343,000 deaths due to liver cancer and 358,000 deaths due to cirrhosis occurred in 2013 due to hepatitis C. The existence of hepatitis C  originally identifiable only as a type of non-A non-B hepatitis  was suggested in the 1970s and proven in 1989. Hepatitis C infects only humans and chimpanzees. Tuberculosis (TB) is an infectious disease caused by the bacterium "Mycobacterium tuberculosis" (MTB). Tuberculosis generally affects the lungs, but can also affect other parts of the body. Most infections do not have symptoms; in which case it is known as latent tuberculosis. About 10% of latent infections progress to active disease which, if left untreated, kills about half of those infected. The classic symptoms of active TB are a chronic cough with blood-containing sputum, fever, night sweats, and weight loss. The historical term "consumption" came about due to the weight loss. Infection of other organs can cause a wide range of symptoms.
  Tuberculosis is spread through the air when people who have active TB in their lungs cough, spit, speak, or sneeze. People with latent TB do not spread the disease. Active infection occurs more often in people with HIV/AIDS and in those who smoke. Diagnosis of active TB is based on chest X-rays, as well as microscopic examination and culture of body fluids. Diagnosis of latent TB relies on the tuberculin skin test (TST) or blood tests.
  Prevention of TB involves screening those at high risk, early detection and treatment of cases, and vaccination with the bacillus Calmette-Guérin vaccine. Those at high risk include household, workplace, and social contacts of people with active TB. Treatment requires the use of multiple antibiotics over a long period of time. Antibiotic resistance is a growing problem with increasing rates of multiple drug-resistant tuberculosis (MDR-TB).
  One-third of the world's population is thought to be infected with TB. New infections occur in about 1% of the population each year. In 2014, there were 9.6 million cases of active TB which resulted in 1.5 million deaths. More than 95% of deaths occurred in developing countries. The number of new cases each year has decreased since 2000. About 80% of people in many Asian and African countries test positive while 510% of people in the United States population tests positive by the tuberculin test. Tuberculosis has been present in humans since ancient times. Liver cancer, also known as hepatic cancer and primary hepatic cancer, is cancer that starts in the liver. Cancer which has spread from elsewhere to the liver, known as liver metastasis, is more common than that which starts in the liver. Symptoms of liver cancer may include a lump or pain in the right side below the rib cage. Other symptoms includes swelling of the abdomen, yellowish skin, easy bruising, weight loss, and weakness.
  The leading cause of liver cancer is cirrhosis due to either hepatitis B, hepatitis C, or alcohol. Other causes include aflatoxin, non-alcoholic fatty liver disease, and liver flukes. The most common types are hepatocellular carcinoma (HCC) which makes up 80% of cases and cholangiocarcinoma. Less common types include mucinous cystic neoplasm and intraductal papillary biliary neoplasm. The diagnosis may be supported by blood tests and medical imaging with confirmation by tissue biopsy.
  Preventive efforts include immunization against hepatitis B and treating those infected with hepatitis B or C. Screening is recommended in those with chronic liver disease. Treatment options may include surgery, targeted therapy, and radiation therapy. In certain cases ablation therapy, embolization therapy, or liver transplantation may be used. Small lumps in the liver may be simply closely followed.
  Primary liver cancer is globally the sixth most frequent cancer (6%) and the second leading cause of death from cancer (9%). In 2012 it occurred in 782,000 people and resulted in 746,000 deaths. In 2013, 300,000 deaths from liver cancer were due to hepatitis B, 343,000 to hepatitis C, and 92,000 to alcohol. Higher rates of liver cancer occur where hepatitis B and C are common, including Asia and sub-Saharan Africa. Males are more often affected with HCC than females. Diagnosis is most frequent among those 55 to 65 years old. Five-year survival rates are 18% in the United States. The word "hepatic" is from the Greek "hêpar", meaning "liver".
  Classification.
  The most frequent liver cancer, accounting for approximately 75% of all primary liver cancers, is hepatocellular carcinoma (HCC) (also named "hepatoma", which is a misnomer because adenomas are usually benign). HCC is a cancer formed by liver cells, known as hepatocytes, that become malignant. Another type of cancer formed by liver cells is hepatoblastoma, which is specifically formed by immature liver cells.<ref name="doi10.1016/j.mpsur.2008.12.005"></ref> It is a rare malignant tumor that primarily develops in children, and accounts for approximately 1% of all cancers in children and 79% of all primary liver cancers under the age of 15. Most hepatoblastomas form in the right lobe. Respiratory tract infection refers to any of a number of infectious diseases involving the respiratory tract. An infection of this type is normally further classified as an upper respiratory tract infection (URI or URTI) or a lower respiratory tract infection (LRI or LRTI). Lower respiratory infections, such as pneumonia, tend to be far more serious conditions than upper respiratory infections, such as the common cold. Diarrhea, also spelled diarrhoea, is the condition of having at least three loose or liquid bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin with loss of the normal stretchiness of the skin and irritable behaviour. This can progress to decreased urination, loss of skin color, a fast heart rate, and a decrease in responsiveness as it becomes more severe. Loose but non-watery stools in babies who are breastfed, however, may be normal.
  The most common cause is an infection of the intestines due to either a virus, bacteria, or parasite; a condition known as gastroenteritis. These infections are often acquired from food or water that has been contaminated by stool, or directly from another person who is infected. It may be divided into three types: short duration watery diarrhea, short duration bloody diarrhea, and if it lasts for more than two weeks, persistent diarrhea. The short duration watery diarrhea may be due to an infection by cholera, although this is rare in the developed world. If blood is present it is also known as dysentery. A number of non-infectious causes may also result in diarrhea, including hyperthyroidism, lactose intolerance, inflammatory bowel disease, a number of medications, and irritable bowel syndrome. In most cases, stool cultures are not required to confirm the exact cause.
  Prevention of infectious diarrhea is by improved sanitation, clean drinking water, and hand washing with soap. Breastfeeding for at least six months is also recommended as is vaccination against rotavirus. Oral rehydration solution (ORS), which is clean water with modest amounts of salts and sugar, is the treatment of choice. Zinc tablets are also recommended. These treatments have been estimated to have saved 50 million children in the past 25 years. When people have diarrhea it is recommended that they continue to eat healthy food and babies continue to be breastfed. If commercial ORS are not available, homemade solutions may be used. In those with severe dehydration, intravenous fluids may be required. Most cases; however, can be managed well with fluids by mouth. Antibiotics, while rarely used, may be recommended in a few cases such as those who have bloody diarrhea and a high fever, those with severe diarrhea following travelling, and those who grow specific bacteria or parasites in their stool. Loperamide may help decrease the number of bowel movements but is not recommended in those with severe disease.
  About 1.7 to 5 billion cases of diarrhea occur per year. It is most common in developing countries, where young children get diarrhea on average three times a year. Total deaths from diarrhea are estimated at 1.26 million in 2013  down from 2.58 million in 1990. In 2012, it was the second most common cause of deaths in children younger than five (0.76 million or 11%). Frequent episodes of diarrhea are also a common cause of malnutrition and the most common cause in those younger than five years of age. Other long term problems that can result include stunted growth and poor intellectual development. A pandemic (from Greek  "pan" "all" and  "demos" "people") is an epidemic of infectious disease that has spread through human populations across a large region; for instance multiple continents, or even worldwide. A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic. Further, flu pandemics generally exclude recurrences of seasonal flu. Throughout history, there have been a number of pandemics, such as smallpox and tuberculosis. One of the most devastating pandemics was the Black Death, killing over 75 million people in 1350. The most recent pandemics include the HIV pandemic as well as the 1918 and 2009 H1N1 pandemics. Gonorrhea, also spelled gonorrhoea, is a sexually transmitted infection caused by the bacterium "Neisseria gonorrhoeae". Many people have no symptoms. Men may have burning with urination, discharge from the penis, or testicular pain. Women may have burning with urination, vaginal discharge, vaginal bleeding between periods, or pelvic pain. Complications in women include pelvic inflammatory disease and in men include inflammation of the epididymis. If untreated gonorrhea can occasionally spread to affect joints or heart valves.
  Gonorrhea is spread through sexual contact with an infected person. This includes oral, anal, and vaginal sex. It can also spread from a mother to a child during birth. Diagnosis is by testing the urine, urethra in males, or cervix in females. Testing all women who are sexually active and less than 25 years of age each year as well as those with new sexual partners is recommended. This same recommendation applies in men who have sex with men.
  Gonorrhea can be prevented with the use of condoms, having sex with only one person who is uninfected, and by not having sex. Treatment is usually with ceftriaxone by injection and azithromycin by mouth. Resistance has developed to many previously used antibiotics and higher doses of ceftriaxone are occasionally required. Retesting is recommended three months after treatment. Sexual partners from the last 2 months should also be treated.
  Gonorrhea affects about 0.8% of women and 0.6% of men. An estimated 33 to 106 million new cases occur each year, out of the 498 million new cases of curable STI  which also includes syphilis, chlamydia, and trichomoniasis. Infections in women most commonly occur when they are young adults. In 2013, it caused about 2,300 deaths, down from 3,200 in 1990. Descriptions of the disease date as far back as the Old Testament. Immunodeficiency (or immune deficiency) is a state in which the immune system's ability to fight infectious disease and cancer is compromised or entirely absent. Most cases of immunodeficiency are acquired ("secondary") due to extrinsic factors that affect the patient's immune system. Examples of these extrinsic factors include HIV infection, extremes of age, and environmental factors, such as nutrition. In the clinical setting, the immunosuppression by some drugs, such as steroids, can be either an adverse effect or the intended purpose of the treatment. Examples of such use is in organ transplant surgery as an anti-rejection measure and in patients suffering from an overactive immune system, as in autoimmune diseases. Some people are born with intrinsic defects in their immune system, or primary immunodeficiency. A person who has an immunodeficiency of any kind is said to be immunocompromised. An immunocompromised person may be particularly vulnerable to opportunistic infections, in addition to normal infections that could affect everyone. Immunodeficiency also decreases cancer immunosurveillance, in which the immune system scans the body's cells and kills neoplastic ones. Postpartum bleeding or postpartum hemorrhage (PPH) is often defined as the loss of more than 500 ml or 1,000 ml of blood within the first 24 hours following childbirth. Some have added the requirement that there also be signs or symptoms of low blood volume for the condition to exist. Signs and symptoms may initially include: an increased heart rate, feeling faint upon standing, and an increased breath rate. As more blood is lost the women may feel cold, their blood pressure may drop, and they may become restless or unconscious. The condition can occur up to six weeks following delivery.
  The most common cause is poor contraction of the uterus following childbirth. Not all of the placenta being delivered, a tear of the uterus, or poor blood clotting are other possible causes. It occurs more commonly in those who: already have a low amount of red blood, are Asian, with bigger or more than one baby, are obese or are older than 40 years of age. It also occurs more commonly following caesarean sections, those in whom medications are used to start labor, and those who have an episiotomy.
  Prevention involves decreasing known risk factors including if possible procedures associated with the condition and giving the medication oxytocin to stimulate the uterus to contract shortly after the baby is born. Misoprostol may be used instead of oxytocin in resource poor settings. Treatments may include: intravenous fluids, blood transfusions, and the medication ergotamine to cause further uterine contraction. Efforts to compress the uterus using the hands may be effective if other treatments do not work. The aorta may also be compressed by pressing on the abdomen. The World Health Organization has recommended non-pneumatic anti-shock garment to help until other measures such as surgery can be carried out.
  In the developing world about 1.2% of deliveries are associated with PPH and when PPH occurred about 3% of women died. Globally it results in 44,000 to 86,000 deaths per year making it the leading cause of death during pregnancy. About 0.4 women per 100,000 deliveries die from PPH in the United Kingdom while about 150 women per 100,000 deliveries die in sub-Saharan Africa. Rates of death have decreased substantially since at least the late 1800s in the United Kingdom.
  Definition.
  Depending on the definition in question, postpartum hemorrhage is defined as more than 500ml following vaginal delivery or 1000ml of blood loss following caesarean section in the first 24 hours following delivery. A prion is an infectious agent composed entirely of protein material, called PrP (short for prion protein), that can fold in multiple, structurally distinct ways, at least one of which is transmissible to other prion proteins, leading to disease that is similar to viral infection. They are suspected to be the cause of transmissible spongiform encephalopathies (TSEs) among other diseases. Childbirth, also known as labour and delivery, is the ending of a pregnancy by one or more babies leaving a woman's uterus. In 2015 there were about 135 million births globally. About 15 million were born before 37 weeks of gestation, while between 3 and 12% were born after 42 weeks. In the developed world most deliveries occur in hospital, while in the developing world most births take place at home with the support of a traditional birth attendant.
  The most common way of childbirth is a vaginal delivery. It involves three stages of labour: the shortening and opening of the cervix, descent and birth of the baby, and the pushing out of the placenta. The first stage typically lasts twelve to nineteen hours, the second stage twenty minutes to two hours, and the third stage five to thirty minutes. The first stage begins with crampy abdominal or back pains that last around half a minute and occur every ten to thirty minutes. The crampy pains become stronger and closer together over time. During the second stage pushing with contractions may occur. In the third stage delayed clamping of the umbilical cord is generally recommended. A number of methods can help with pain such as relaxation techniques, opioids, and spinal blocks.
  Most babies are born head first; however about 4% are born feet or buttock first, known as breech. During labour a woman can generally eat and move around as she likes, but pushing is not recommended during the first stage or during delivery of the head, and enemas are not recommended. While making a cut to the opening of the vagina is common, known as an episiotomy, it is generally not needed. In 2012, about 23 million deliveries occurred by a surgical procedure known as Caesarean section. Caesarean sections may be recommended for twins, signs of distress in the baby, or breech position. This method of delivery can take longer to heal from.
  Each year complications from pregnancy and childbirth result in about 500,000 maternal deaths, 7 million women have serious long term problems, and 50 million women have health negative outcomes following delivery. Most of these occur in the developing world. Specific complications include obstructed labour, postpartum bleeding, eclampsia, and postpartum infection. Complications in the baby include birth asphyxia. A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as kidney infection (pyelonephritis). Symptoms from a lower urinary tract include pain with urination, frequent urination, and feeling the need to urinate despite having an empty bladder. Symptoms of a kidney infection include fever and flank pain usually in addition to the symptoms of a lower UTI. Rarely the urine may appear bloody. In the very old and the very young, symptoms may be vague or non-specific.
  The most common cause of infection is "Escherichia coli", though other bacteria or fungi may rarely be the cause. Risk factors include female anatomy, sexual intercourse, diabetes, obesity, and family history. Although sexual intercourse is a risk factor, UTIs are not classified as sexually transmitted infections (STIs). Kidney infection, if it occurs, usually follows a bladder infection but may also result from a blood-borne infection. Diagnosis in young healthy women can be based on symptoms alone. In those with vague symptoms, diagnosis can be difficult because bacteria may be present without there being an infection. In complicated cases or if treatment fails, a urine culture may be useful.
  In uncomplicated cases, UTIs are treated with a short course of antibiotics such as nitrofurantoin or trimethoprim/sulfamethoxazole. Resistance to many of the antibiotics used to treat this condition is increasing. In complicated cases, a longer course or intravenous antibiotics may be needed. If symptoms do not improved in two or three days, further diagnostic testing may be needed. Phenazopyridine may help with symptoms. In those who have bacteria or white blood cells in their urine but have no symptoms, antibiotics are generally not needed, although during pregnancy is an exception. In those with frequent infections, a short course of antibiotics may be taken as soon as symptoms begin or long term antibiotics may be used as a preventative measure.
  About 150 million people developed a urinary tract infection each year. They are more common in women than men. In women, they are the most common form of bacterial infection. Up to 10% of women have a urinary tract infection in a given year and half of women having at least one infection at some point in their lives. They occur most frequently between the ages of 16 and 35 years. Recurrences are common. Urinary tract infections have been described since ancient times with the first documented description in the Ebers Papyrus dated to c. 1550 BC.
  Signs and symptoms.
  Lower urinary tract infection is also referred to as a bladder infection. The most common symptoms are burning with urination and having to urinate frequently (or an urge to urinate) in the absence of vaginal discharge and significant pain. These symptoms may vary from mild to severe and in healthy women last an average of six days. Some pain above the pubic bone or in the lower back may be present. People experiencing an upper urinary tract infection, or pyelonephritis, may experience flank pain, fever, or nausea and vomiting in addition to the classic symptoms of a lower urinary tract infection. Rarely the urine may appear bloody or contain visible pus in the urine. Hepatitis B is an infectious disease caused by the hepatitis B virus (HBV) which affects the liver. It can cause both acute and chronic infections. Many people have no symptoms during the initial infection. Some develop a rapid onset of sickness with vomiting, yellowish skin, tiredness, dark urine and abdominal pain. Often these symptoms last a few weeks and rarely does the initial infection result in death. It may take 30 to 180 days for symptoms to begin. In those who get infected around the time of birth 90% develop chronic while less than 10% of those infected after the age of five do. Most of those with chronic disease have no symptoms; however, cirrhosis and liver cancer may eventually develop. These complications result in the death of 15 to 25% of those with chronic disease.
  The virus is transmitted by exposure to infectious blood or body fluids. Infection around the time of birth or from contact with other people's blood during childhood is the most frequent method by which hepatitis B is acquired in areas where the disease is common. In areas where the disease is rare, intravenous drug use and sexual intercourse are the most frequent routes of infection. Other risk factors include working in healthcare, blood transfusions, dialysis, living with an infected person, travel in countries where the infection rate is high, and living in an institution. Tattooing and acupuncture led to a significant number of cases in the 1980s; however, this has become less common with improved sterility. The viruses cannot be spread by holding hands, sharing eating utensils, kissing, hugging, coughing, sneezing, or breastfeeding. The infection can be diagnosed 30 to 60 days after exposure. The diagnosis is usually confirmed by testing the blood for parts of the virus and for antibodies against the virus. It is one of five known hepatitis viruses: A, B, C, D, and E.
  The infection has been preventable by vaccination since 1982. Vaccination is recommended by the World Health Organization in the first day of life if possible. Two or three more doses are required at a later time for full effect. This vaccine works about 95% of the time. About 180 countries gave the vaccine as part of national programs as of 2006. It is also recommended that all blood be tested for hepatitis B before transfusion and condoms be used to prevent infection. During an initial infection, care is based on the symptoms that a person has. In those who develop chronic disease, antiviral medication such as tenofovir or interferon may be useful; however, these drugs are expensive. Liver transplantation is sometimes used for cirrhosis.
  About a third of the world population has been infected at one point in their lives, including 240 million to 350 million who have chronic infections. Another 129 million new infections occurred in 2013. Over 750,000 people die of hepatitis B each year. About 300,000 of these are due to liver cancer. The disease is now only common in East Asia and sub-Saharan Africa where between 5 and 10% of adults are chronically infected. Rates in Europe and North America are less than 1%. It was originally known as "serum hepatitis". Research is looking to create foods that contain HBV vaccine. The disease may affect other great apes as well.
  Signs and symptoms.
  Acute infection with virus is associated with acute viral hepatitis, an illness that begins with general ill-health, loss of appetite, nausea, vomiting, body aches, mild fever, and dark urine, and then progresses to development of jaundice. It has been noted that itchy skin has been an indication as a possible symptom of all hepatitis virus types. The illness lasts for a few weeks and then gradually improves in most affected people. A few people may have a more severe form of liver disease known as (fulminant hepatic failure) and may die as a result. The infection may be entirely asymptomatic and may go unrecognized. Male circumcision is the removal of the foreskin from the human penis. In the most common procedure, the foreskin is opened, adhesions are removed, and the foreskin is separated from the glans. After that, the circumcision device (if used) is placed, and then the foreskin is cut off. Topical or locally injected anesthesia is occasionally used to reduce pain and physiologic stress. For adults and children, general anesthesia is an option, and the procedure may be performed without a specialized circumcision device. The procedure is most often an elective surgery performed on babies and children for religious and cultural reasons. In other cases it may be done as a treatment for a condition or for preventative reasons. Medically, it is a treatment option for problematic cases of phimosis, balanoposthitis that does not resolve with other treatments, and chronic urinary tract infections (UTIs). It is contraindicated in cases of certain genital structure abnormalities or poor general health.
  The positions of the world's major medical organizations range from considering elective circumcision of babies and children as having no benefit and significant risks to having a modest health benefit that outweighs small risks. No major medical organization recommends either universal circumcision for all males (aside from the recommendations of the World Health Organization (WHO) for areas with high rates of HIV), or banning the procedure. Ethical and legal questions regarding informed consent and human rights have been raised over the circumcision of babies and children for non-medical reasons, and for that reason the procedure is controversial.
  Evidence supports that male circumcision reduces the risk of HIV infection among heterosexual men in sub-Saharan Africa. Therefore, the WHO recommends considering circumcision as part of a comprehensive HIV prevention program in areas with high rates of HIV, such as Sub Saharan Africa. Evidence for a health benefit against HIV for men who have sex with men is less clear. Additionally, the effectiveness of using circumcision to prevent HIV in the developed world is also unclear. Circumcision in general is associated with reduced rates of cancer causing forms of HPV and risk of both UTIs and cancer of the penis. Prevention of those conditions is not a justification for routine circumcision of infants. Studies of its potential protective effects against other sexually transmitted infections have been unclear. A 2010 review of literature found circumcisions performed by medical providers to have a typical complication rate of 1.5% for babies and 6% for older children, with few cases of severe complications. Bleeding, infection and the removal of either too much or too little foreskin are the most common complications cited. Complication rates are higher when the procedure is performed by an inexperienced operator, in unsterile conditions, or when the child is at an older age. Circumcision does not appear to have a negative impact on sexual function.
  An estimated one-third of males worldwide are circumcised. The procedure is most common in the Muslim world and Israel (where it is near-universal for religious reasons), the United States, and parts of Southeast Asia and Africa. It is relatively rare in Europe, Latin America, parts of Southern Africa, and most of Asia. The origin of circumcision is not known with certainty; the oldest documented evidence for it comes from ancient Egypt. Various theories have been proposed as to its origin, including as a religious sacrifice and as a rite of passage marking a boy's entrance into adulthood. It is part of religious law in Judaism and is an established practice in Islam, Coptic Christianity, and the Ethiopian Orthodox Church. The word circumcision is from Latin "circumcidere", meaning "to cut around".  In the practice of medicine (especially surgery and dentistry), anesthesia or anaesthesia is a temporary induced loss of sensation or awareness. It may include analgesia (relief from or prevention of pain), paralysis (muscle relaxation), amnesia (loss of memory), or unconsciousness. A patient under the effects of anesthetic drugs is referred to as being anesthetized. Pathology (from the Greek roots of "pathos", meaning "experience" or "suffering", and "-logia", "study of") is a significant component of the causal study of disease and a major field in modern medicine and diagnosis. The placenta (also known as afterbirth) is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, provide thermo-regulation to the fetus, waste elimination, and gas exchange via the mother's blood supply, fight against internal infection and produce hormones to support pregnancy. The placenta provides oxygen and nutrients to growing babies and removes waste products from the baby's blood. The placenta attaches to the wall of the uterus, and the baby's umbilical cord develops from the placenta. The umbilical cord is what connects the mother and the baby. Placentas are a defining characteristic of placental mammals, but are also found in some non-mammals with varying levels of development. The homology of such structures in various viviparous organisms is debatable, and in invertebrates such as Arthropoda, is analogous at best. Elective surgery or elective procedure (from the Latin "eligere", meaning to choose) is surgery that is scheduled in advance because it does not involve a medical emergency. Semi-elective surgery is a surgery that must be done to preserve the patient's life, but does not need to be performed immediately. Macroparasites are parasites that are large enough to be seen with the naked eye, in contrast to microparasites. They grow in one host but reproduce by infective stages outside this host. These generally include ticks, mites, helminths (nematodes, flatworms, etc.), and can be either external parasites (ectoparasitic) or internal parasites (endoparasitic). The most abundant macroparasite in humans is the nematode "Ascaris lumbricoides "which causes an infection called ascariasis. Macroparasites are also parasitic of many plant species and can be a significant agricultural pest. Hepatitis A (formerly known as infectious hepatitis) is an infectious disease of the liver caused by the hepatitis A virus (HAV). Many cases have few or no symptoms, especially in the young. The time between infection and symptoms, in those who develop them, is between two and six weeks. When symptoms occur, they typically last eight weeks and may include nausea, vomiting, diarrhea, jaundice, fever, and abdominal pain. Around 1015% of people experience a recurrence of symptoms during the six months after the initial infection. Acute liver failure may rarely occur, with this being more common in the elderly.
  It is usually spread by eating food or drinking water contaminated with infected feces. Shellfish which have not been sufficiently cooked are a relatively common source. It may also be spread through close contact with an infectious person. While children often do not have symptoms when infected, they are still able to infect others. After a single infection, a person is immune for the rest of his or her life. Diagnosis requires blood testing, as the symptoms are similar to those of a number of other diseases. It is one of five known hepatitis viruses: A, B, C, D, and E.
  The hepatitis A vaccine is effective for prevention. Some countries recommend it routinely for children and those at higher risk who have not previously been vaccinated. It appears to be effective for life. Other preventive measures include hand washing and properly cooking food. No specific treatment is available, with rest and medications for nausea or diarrhea recommended on an as-needed basis. Infections usually resolve completely and without ongoing liver disease. Treatment of acute liver failure, if it occurs, is with liver transplantation.
  Globally, around 1.4 million symptomatic cases occur each year and about 102 million infections (symptomatic and asymptomatic). It is more common in regions of the world with poor sanitation and not enough safe water. In the developing world about 90% of children have been infected by age 10 and thus are immune by adulthood. It often occurs in outbreaks in moderately developed countries where children are not exposed when young and vaccination is not widespread. Acute hepatitis A resulted in 102,000 deaths in 2010. World Hepatitis Day occurs each year on July 28 to bring awareness to viral hepatitis. Yaws is a tropical infection of the skin, bones and joints caused by the spirochete bacterium "Treponema pallidum pertenue". The disease begins with a round, hard swelling of the skin, 2 to 5 centimeters in diameter. The center may break open and form an ulcer. This initial skin lesion typically heals after three to six months. After weeks to years, joints and bones may become painful, fatigue may develop, and new skin lesions may appear. The skin of the palms of the hands and the soles of the feet may become thick and break open. The bones (especially those of the nose) may become misshapen. After five years or more large areas of skin may die, leaving a scar.
  Yaws is spread by direct contact with the fluid from a lesion of an infected person. The contact is usually of a non-sexual nature. The disease is most common among children, who spread it by playing together. Other related treponemal diseases are bejel ("Treponema pallidum endemicum"), pinta ("Treponema pallidum carateum"), and syphilis ("Treponema pallidum pallidum"). Yaws is often diagnosed by the appearance of the lesions. Blood antibody tests may be useful but cannot separate previous from current infections. Polymerase chain reaction (PCR) is the most accurate method of diagnosis.
  Prevention is, in part, by curing those who have the disease thereby decreasing the risk of transmission. Where the disease is common, treating the entire community is effective. Improving cleanliness and sanitation will also decrease spread. Treatment is typically with antibiotics including: azithromycin by mouth or benzathine penicillin by injection. Without treatment, physical deformities occur in 10% of cases.
  Yaws is common in at least 14 tropical countries as of 2012. The disease infects only humans. In the 1950s and 1960s the World Health Organization (WHO) nearly eradicated yaws. Since then the number of cases has increased and there are renewed efforts to globally eradicate the disease by 2020. The last estimate of the number of people infected was more than 500,000 in 1995. Although one of the first descriptions of the disease was made in 1679 by Willem Piso, archaeological evidence suggests that yaws may have been present among humans as far back as 1.6 million years ago. Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. Not all tumors are cancerous; benign tumors do not spread to other parts of the body. Possible signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss and a change in bowel movements. While these symptoms may indicate cancer, they may have other causes. Over 100 types of cancers affect humans.
  Tobacco use is the cause of about 22% of cancer deaths. Another 10% is due to obesity, poor diet, lack of physical activity and drinking alcohol. Other factors include certain infections, exposure to ionizing radiation and environmental pollutants. In the developing world nearly 20% of cancers are due to infections such as hepatitis B, hepatitis C and human papillomavirus (HPV). These factors act, at least partly, by changing the genes of a cell. Typically many genetic changes are required before cancer develops. Approximately 510% of cancers are due to inherited genetic defects from a person's parents. Cancer can be detected by certain signs and symptoms or screening tests. It is then typically further investigated by medical imaging and confirmed by biopsy.
  Many cancers can be prevented by not smoking, maintaining a healthy weight, not drinking too much alcohol, eating plenty of vegetables, fruits and whole grains, vaccination against certain infectious diseases, not eating too much processed and red meat, and avoiding too much sunlight exposure. Early detection through screening is useful for cervical and colorectal cancer. The benefits of screening in breast cancer are controversial. Cancer is often treated with some combination of radiation therapy, surgery, chemotherapy, and targeted therapy. Pain and symptom management are an important part of care. Palliative care is particularly important in people with advanced disease. The chance of survival depends on the type of cancer and extent of disease at the start of treatment. In children under 15 at diagnosis the five-year survival rate in the developed world is on average 80%. For cancer in the United States the average five-year survival rate is 66%.
  In 2012 about 14.1 million new cases of cancer occurred globally (not including skin cancer other than melanoma). It caused about 8.2 million deaths or 14.6% of human deaths. The most common types of cancer in males are lung cancer, prostate cancer, colorectal cancer and stomach cancer. In females, the most common types are breast cancer, colorectal cancer, lung cancer and cervical cancer. If skin cancer other than melanoma were included in total new cancers each year it would account for around 40% of cases. In children, acute lymphoblastic leukaemia and brain tumors are most common except in Africa where non-Hodgkin lymphoma occurs more often. In 2012, about 165,000 children under 15 years of age were diagnosed with cancer. The risk of cancer increases significantly with age and many cancers occur more commonly in developed countries. Rates are increasing as more people live to an old age and as lifestyle changes occur in the developing world. The financial costs of cancer were estimated at $1.16 trillion US dollars per year as of 2010.
  Definitions.
  Cancers are a large family of diseases that involve abnormal cell growth with the potential to invade or spread to other parts of the body. They form a subset of neoplasms. A neoplasm or tumor is a group of cells that have undergone unregulated growth and will often form a mass or lump, but may be distributed diffusely. Trichomonas vaginalis is an anaerobic, flagellated protozoan parasite and the causative agent of trichomoniasis. It is the most common pathogenic protozoan infection of humans in industrialized countries. Infection rates between men and women are similar with women being symptomatic, while infections in men are usually asymptomatic. Transmission usually occurs via direct, skin-to-skin contact with an infected individual, most often through vaginal intercourse. The WHO has estimated that 160 million cases of infection are acquired annually worldwide. The estimates for North America alone are between 5 and 8 million new infections each year, with an estimated rate of asymptomatic cases as high as 50%. Usually treatment consists of metronidazole and tinidazole. Neurosyphilis is an infection of the brain or spinal cord caused by the spirochete "Treponema pallidum". It usually occurs in people who have had chronic, untreated syphilis, usually about 10 to 20 years after first infection and develops in about 25%40% of persons who are not treated. The United States' Centers for Disease Control and Prevention (CDC) advises that neurosyphilis can occur at any stage of a syphilis infection. Hepatitis is inflammation of the liver. Some people have no symptoms whereas others develop yellow discoloration of the skin and whites of the eyes, poor appetite, vomiting, tiredness, abdominal pain, or diarrhea. Hepatitis may be temporary (acute) or long term (chronic) depending on whether it lasts for less than or more than six months. Acute hepatitis can sometimes resolve on its own, progress to chronic hepatitis, or rarely result in acute liver failure. Over time the chronic form may progress to scarring of the liver, liver failure, or liver cancer.
  The most common cause worldwide is viruses. Other causes include heavy alcohol use, certain medications, toxins, other infections, autoimmune diseases, and non-alcoholic steatohepatitis (NASH). There are five main types of viral hepatitis: type A, B, C, D, and E. Hepatitis A and E are mainly spread by contaminated food and water. Hepatitis B is mainly sexually transmitted, but may also be passed from mother to baby during pregnancy or childbirth. Both hepatitis B and hepatitis C are commonly spread through infected blood such as may occur during needle sharing by intravenous drug users. Hepatitis D can only infect people already infected with hepatitis B.
  Hepatitis A, B, and D are preventable with immunization. Medications may be used to treat chronic cases of viral hepatitis. There is no specific treatment for NASH; however, a healthy lifestyle, including physical activity, a healthy diet, and weight loss, is important. Autoimmune hepatitis may be treated with medications to suppress the immune system. A liver transplant may also be an option in certain cases.
  Worldwide in 2015, hepatitis A occurred in about 114 million people, chronic hepatitis B affected about 343 million people and chronic hepatitis C about 142 million people. In the United States, NASH affects about 11 million people and alcoholic hepatitis affects about 5 million people. Hepatitis results in more than a million deaths a year, most of which occur indirectly from liver scarring or liver cancer. In the United States, hepatitis A is estimated to occur in about 2,500 people a year and results in about 75 deaths. The word is derived from the Greek "hêpar", meaning "liver", and "-itis", meaning "inflammation".  Breastfeeding, also known as nursing, is the feeding of babies and young children with milk from a woman's breast. Health professionals recommend that breastfeeding begin within the first hour of a baby's life and continue as often and as much as the baby wants. During the first few weeks of life babies may nurse roughly every two to three hours. The duration of a feeding is usually ten to fifteen minutes on each breast. Older children feed less often. Mothers may pump milk so that it can be used later when breastfeeding is not possible. Breastfeeding has a number of benefits to both mother and baby, which infant formula lacks.
  Deaths of an estimated 820,000 children under the age of five could be prevented globally every year with increased breastfeeding. Breastfeeding decreases the risk of respiratory tract infections and diarrhea, both in developing and developed countries. Other benefits include lower risks of asthma, food allergies, celiac disease, type 1 diabetes, and leukemia. Breastfeeding may also improve cognitive development and decrease the risk of obesity in adulthood. Mothers may feel pressure to breastfeed; however in the developed world children generally grow up normally when bottle feed.
  Benefits for the mother include less blood loss following delivery, better uterus shrinkage, weight loss, and less postpartum depression. Breastfeeding delays the return of menstruation and fertility, a phenomenon known as lactational amenorrhea. Long term benefits for the mother include decreased risk of breast cancer, cardiovascular disease, and rheumatoid arthritis. Breastfeeding is often less expensive than infant formula.
  Health organizations, including the World Health Organization (WHO), recommend breastfeeding exclusively for six months. This means that no other foods or drinks other than possibly vitamin D are typically given. After the introduction of foods at six months of age, recommendations include continued breastfeeding until at least one to two years of age. Globally about 38% of infants are only breastfed during their first six months of life. In the United States, about 75% of women begin breastfeeding and about 13% only breastfeed until the age of six months. Medical conditions that do not allow breastfeeding are rare. Mothers who take certain recreational drugs and medications should not breastfeed. Smoking, limited intake of alcohol, and coffee are not reasons to avoid breastfeeding. Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, fluid coming from the nipple, or a red scaly patch of skin. In those with distant spread of the disease, there may be bone pain, swollen lymph nodes, shortness of breath, or yellow skin.
  Risk factors for developing breast cancer include being female, obesity, lack of physical exercise, drinking alcohol, hormone replacement therapy during menopause, ionizing radiation, early age at first menstruation, having children late or not at all, older age, and family history. About 510% of cases are due to genes inherited from a person's parents, including BRCA1 and BRCA2 among others. Breast cancer most commonly develops in cells from the lining of milk ducts and the lobules that supply the ducts with milk. Cancers developing from the ducts are known as ductal carcinomas, while those developing from lobules are known as lobular carcinomas. In addition, there are more than 18 other sub-types of breast cancer. Some cancers, such as ductal carcinoma in situ, develop from pre-invasive lesions. The diagnosis of breast cancer is confirmed by taking a biopsy of the concerning lump. Once the diagnosis is made, further tests are done to determine if the cancer has spread beyond the breast and which treatments it may respond to.
  The balance of benefits versus harms of breast cancer screening is controversial. A 2013 Cochrane review stated that it is unclear if mammographic screening does more good or harm. A 2009 review for the US Preventive Services Task Force found evidence of benefit in those 40 to 70 years of age, and the organization recommends screening every two years in women 50 to 74 years old. The medications tamoxifen or raloxifene may be used in an effort to prevent breast cancer in those who are at high risk of developing it. Surgical removal of both breasts is another preventative measure in some high risk women. In those who have been diagnosed with cancer, a number of treatments may be used, including surgery, radiation therapy, chemotherapy, hormonal therapy and targeted therapy. Types of surgery vary from breast-conserving surgery to mastectomy. Breast reconstruction may take place at the time of surgery or at a later date. In those in whom the cancer has spread to other parts of the body, treatments are mostly aimed at improving quality of life and comfort.
  Outcomes for breast cancer vary depending on the cancer type, extent of disease, and person's age. Survival rates in the developed world are high, with between 80% and 90% of those in England and the United States alive for at least 5 years. In developing countries survival rates are poorer. Worldwide, breast cancer is the leading type of cancer in women, accounting for 25% of all cases. In 2012 it resulted in 1.68 million cases and 522,000 deaths. It is more common in developed countries and is more than 100 times more common in women than in men. The human immunodeficiency virus (HIV) is a lentivirus (a subgroup of retrovirus) that causes HIV infection and over time acquired immunodeficiency syndrome (AIDS). AIDS is a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive. Without treatment, average survival time after infection with HIV is estimated to be 9 to 11 years, depending on the HIV subtype. Infection with HIV occurs by the transfer of blood, semen, vaginal fluid, pre-ejaculate, or breast milk. Within these bodily fluids, HIV is present as both free virus particles and virus within infected immune cells. A retrovirus is a single-stranded positive-sense RNA virus with a DNA intermediate and, as an obligate parasite, targets a host cell. Once inside the host cell cytoplasm, the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern, thus "retro" (backwards). The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is referred to as a provirus. The host cell then treats the viral DNA as part of its own genome, translating and transcribing the viral genes along with the cell's own genes, producing the proteins required to assemble new copies of the virus. It is difficult to detect the virus until it has infected the host. At that point, the infection will persist indefinitely. Obstructed labour, also known as labour dystocia, is when, even though the uterus is contracting normally, the baby does not exit the pelvis during childbirth due to being physically blocked. Complications for the baby include not getting enough oxygen which may result in death. It increases the risk of the mother getting an infection, having uterine rupture, or having post-partum bleeding. Long term complications for the mother include obstetrical fistula. Obstructed labour is said to result in prolonged labour, when the active phase of labour is longer than twelve hours.
  The main causes of obstructed labour include: a large or abnormally positioned baby, a small pelvis, and problems with the birth canal. Abnormal positioning includes shoulder dystocia where the anterior shoulder does not pass easily below the pubic bone. Risk factors for a small pelvis include malnutrition and a lack of exposure to sunlight causing vitamin D deficiency. It is also more common in adolescence as the pelvis may not have finished growing. Problems with the birth canal include a narrow vagina and perineum which may be due to female genital mutilation or tumors. A partograph is often used to track labour progression and diagnose problems. This combined with physical examination may identify obstructed labour.
  The treatment of obstructed labour may require cesarean section or vacuum extraction with possible surgical opening of the symphysis pubis. Other measures include: keeping the women hydrated and antibiotics if the membranes have been ruptured for more than 18 hours. In Africa and Asia obstructed labor effects between two and five percent of deliveries. In 2013 about 5.1 cases of obstructed labour occurred. This resulted in 19,000 deaths down from 29,000 deaths in 1990 (about 8% of all deaths related to pregnancy). Most deaths due to this condition occur in the developing world. Bacterial vaginosis (BV) is a disease of the vagina caused by excessive growth of bacteria. Common symptoms include increased vaginal discharge that often smells like fish. The discharge is usually white or gray in color. Burning with urination may occur. Itching is uncommon. Occasionally, there may be no symptoms. Having BV approximately doubles the risk of infection by a number of other sexually transmitted infections, including HIV/AIDS. It also increases the risk of early delivery among pregnant women.
  BV is caused by an imbalance of the naturally occurring bacteria in the vagina. There is a change in the most common type of bacteria and a hundred to thousandfold increase in total numbers of bacteria present. Typically, bacteria other than "Lactobacilli" become more common. Risk factors include douching, new or multiple sex partners, antibiotics, and using an intrauterine device, among others. However, it is not considered a sexually transmitted infection. Diagnosis is suspected based on the symptoms, and may be verified by testing the vaginal discharge and finding a higher than normal vaginal pH, and large numbers of bacteria. BV is often confused with a vaginal yeast infection or infection with Trichomonas.
  Usually treatment is with an antibiotic, such as clindamycin or metronidazole. These medications may also be used in the second or third trimesters of pregnancy. However, the condition often recurs following treatment. Probiotics may help prevent re-occurrence. It is unclear if the use of probiotics or antibiotics affects pregnancy outcomes.
  BV is the most common vaginal infection in women of reproductive age. The percentage of women affected at any given time varies between 5% and 70%. BV is most common in parts of Africa and least common in Asia and Europe. In the United States about 30% of women between the ages of 14 and 49 are affected. Rates vary considerably between ethnic groups within a country. While BV like symptoms have been described for much of recorded history, the first clearly documented case occurred in 1894. Syphilis is a sexually transmitted infection caused by the bacterium "Treponema pallidum" subspecies "pallidum". The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, and tertiary). The primary stage classically presents with a single chancre (a firm, painless, non-itchy skin ulceration) but there may be multiple sores. In secondary syphilis a diffuse rash occurs, which frequently involves the palms of the hands and soles of the feet. There may also be sores in the mouth or vagina. In latent syphilis, which can last for years, there are few or no symptoms. In tertiary syphilis there are gummas (soft non-cancerous growths), neurological, or heart symptoms. Syphilis has been known as "the great imitator" as it may cause symptoms similar to many other diseases.
  Syphilis is most commonly spread through sexual activity. It may also be transmitted from mother to baby during pregnancy or at birth, resulting in congenital syphilis. Other human diseases caused by related "Treponema pallidum" subspecies include yaws (subspecies "pertenue"), pinta (subspecies "carateum"), and bejel (subspecies "endemicum"). Diagnosis is usually made by using blood tests; the bacteria can also be detected using dark field microscopy. The Center for Disease Control recommends all pregnant women be tested.
  The risk of syphilis can be decreased by latex condom use, or not having sex. Syphilis can be effectively treated with antibiotics. The preferred antibiotic for most cases is benzathine penicillin G injected into a muscle. In those who have a severe penicillin allergy, doxycycline or tetracycline may be used. In those with neurosyphilis, intravenous penicillin G potassium or ceftriaxone is recommended. During treatment people may develop fever, headache, and muscle pains, a reaction known as Jarisch-Herxheimer.
  In 2012, about 0.5% of adults were infected with syphilis with 6 million new cases. During 2010, it caused about 113,000 deaths, down from 202,000 in 1990. After decreasing dramatically with the availability of penicillin in the 1940s, rates of infection have increased since the turn of the millennium in many countries, often in combination with human immunodeficiency virus (HIV). This is believed to be partly due to increased promiscuity, prostitution, decreasing use of condoms, and unsafe sexual practices among men who have sex with men. In 2015, Cuba became the first country in the world to eliminate mother-to-child transmission of syphilis.
  Signs and symptoms.
  Syphilis can present in one of four different stages: primary, secondary, latent, and tertiary, and may also occur congenitally. It was referred to as "the great imitator" by Sir William Osler due to its varied presentations. A disease is a particular abnormal condition, a disorder of a structure or function, that affects part or all of an organism. The study of disease is called pathology which includes the causal study of etiology. Disease is often construed as a medical condition associated with specific symptoms and signs. It may be caused by external factors such as pathogens, or it may be caused by internal dysfunctions particularly of the immune system such as an immunodeficiency, or a hypersensitivity including allergies and autoimmunity. Influenza-like illness (ILI), also known as acute respiratory infection (ARI) and flu-like syndrome/symptoms, is a medical diagnosis of "possible" influenza or other illness causing a set of common symptoms. Sexually transmitted infections ( STI ) , also referred to as sexually transmitted diseases ( STD ) and venereal diseases ( VD ) , are infections that are commonly spread by sex , especially vaginal intercourse , anal sex and oral sex . Most STIs initially do not cause symptoms . This results in a greater risk of passing the disease on to others . Symptoms and signs of disease may include vaginal discharge , penile discharge , ulcers on or around the genitals , and pelvic pain . STIs acquired before or during birth may result in poor outcomes for the baby . Some STIs may cause problems with the ability to get pregnant . More than 30 different bacteria , viruses , and parasites can cause STIs . Bacterial STIs include chlamydia , gonorrhea , and syphilis among others . Viral STIs include genital herpes , HIV / AIDS , and genital warts among others . Parasitic STIs include trichomoniasis among others . While usually spread by sex , some STIs can also be spread by non-sexual contact with contaminated blood and tissues , breastfeeding , or during childbirth . STI diagnostic tests are easily available in the developed world , but this is often not the case in the developing world . The most effective way of preventing STIs is by not having sex . Some vaccinations may also decrease the risk of certain infections including hepatitis B and some types of HPV . Safer sex practices such as use of condoms , having a smaller number of sexual partners , and being in a relationship where each person only has sex with the other also decreases the risk . Circumcision in males may be effective to prevent some infections . Most STIs are treatable or curable . Of the most common infections , syphilis , gonorrhea , chlamydia , trichomoniasis are curable , while herpes , hepatitis B , HIV / AIDS , and HPV are treatable but not curable . Resistance to certain antibiotics is developing among some organisms such as gonorrhea . In 2008 , it was estimated that 500 million people were infected with either syphilis , gonorrhea , chlamydia or trichomoniasis . At least an additional 530 million people have genital herpes and 290 million women have human papillomavirus . STIs other than HIV resulted in 142,000 deaths in 2013 . In the United States there were 19 million new cases of sexually transmitted infections in 2010 . Historical documentation of STIs date back to at least the Ebers papyrus around 1550 BC and the Old Testament . There is often shame and stigma associated with these infections . The term sexually transmitted infection is generally preferred over the terms sexually transmitted disease and venereal disease , as it includes those who do not have symptomatic disease . Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are involved, with the same joints typically involved on both sides of the body. The disease may also affect other parts of the body. This may result in a low red blood cell count, inflammation around the lungs, and inflammation around the heart. Fever and low energy may also be present. Often, symptoms come on gradually over weeks to months.
  While the cause of rheumatoid arthritis is not clear, it is believed to involve a combination of genetic and environmental factors. The underlying mechanism involves the body's immune system attacking the joints. This results in inflammation and thickening of the joint capsule. It also affects the underlying bone and cartilage. The diagnosis is made mostly on the basis of a person's signs and symptoms. X-rays and laboratory testing may support a diagnosis or exclude other diseases with similar symptoms. Other diseases that may present similarly include systemic lupus erythematosus, psoriatic arthritis, and fibromyalgia among others.
  The goal of treatment is to reduce pain, decrease inflammation, and improve a person's overall functioning. This may be helped by balancing rest and exercise, the use of splints and braces, or the use of assistive devices. Pain medications, steroids, and NSAIDs are frequently used to help with symptoms. A group of medications called disease-modifying antirheumatic drugs (DMARDs), such as hydroxychloroquine and methotrexate, may be used to try to slow the progression of disease. Biological DMARDs may be used when disease does not respond to other treatments. However, they may have a greater rate of adverse effects. Surgery to repair, replace, or fuse joints may help in certain situations. Most alternative medicine treatments are not supported by evidence.
  RA affects between 0.5 and 1% of adults in the developed world with between 5 and 50 per 100,000 people newly developing the condition each year. Onset is most frequent during middle age and women are affected 2.5 times as frequently as men. In 2013, it resulted in 38,000 deaths up from 28,000 deaths in 1990. The first recognized description of RA was made in 1800 by Dr. Augustin Jacob Landré-Beauvais (17721840) of Paris. The term "rheumatoid arthritis" is based on the Greek for watery and inflamed joints.
  Signs and symptoms.
  RA primarily affects joints, but it also affects other organs in more than 1525% of individuals. Genital herpes is a genital infection caused by the herpes simplex virus (HSV). Most individuals carrying herpes are unaware they have been infected and many will never suffer an outbreak, which involves blisters similar to cold sores. While there is no cure for herpes, over time symptoms are increasingly mild and outbreaks are decreasingly frequent. When symptomatic, the typical manifestation of a primary infection is clusters of genital sores consisting of inflamed papules and vesicles on the outer surface of the genitals, resembling cold sores. These usually appear 47 days after sexual exposure to HSV for the first time. Genital HSV-1 infection recurs at rate of about one sixth of that of genital HSV-2. Trichomoniasis is an infectious disease caused by the parasite "Trichomonas vaginalis". About 70% of women and men do not have symptoms when infected. When symptoms do occur they typically begin 5 to 28 days after exposure. Symptoms can include itching in the genital area, a bad smelling thin vaginal discharge, burning with urination, and pain with sex. Having trichomoniasis increases the risk of getting HIV/AIDS. It may also cause complications during pregnancy.
  Trichomoniasis is a sexually transmitted infection (STI) which is most often spread through vaginal, oral, or anal sex. It can also spread through genital touching. People who are infected may spread the disease even when symptoms are not present. Diagnosis is by finding the parasite in the vaginal fluid using a microscope, culturing the vagina or urine, or testing for the parasites DNA. If present other sexually transmitted infections should be tested for.
  Methods of prevention include not having sex, using condoms, not douching, and being tested for STIs before having sex with a new partner. Trichomoniasis can be cured with antibiotics, either metronidazole or tinidazole. Sexual partners should also be treated. About 20% of people get infected again within three months of treatment.
  There were about 58 million cases of trichomoniasis in 2013. In the United States there are about 2 million women affected. It occurs more often in women than men. "Trichomonas vaginalis" was first identified in 1836 by Alfred Donné. It was first recognized as causing this disease in 1916. Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have a negative effect on health. People are generally considered obese when their body mass index (BMI), a measurement obtained by dividing a person's weight by the square of the person's height, is over , with the range defined as overweight. Some East Asian countries use lower values. Obesity increases the likelihood of various diseases, particularly heart disease, type 2 diabetes, obstructive sleep apnea, certain types of cancer, and osteoarthritis.
  Obesity is most commonly caused by a combination of excessive food intake, lack of physical activity, and genetic susceptibility. A few cases are caused primarily by genes, endocrine disorders, medications, or mental illness. The view that obese people eat little yet gain weight due to a slow metabolism is not generally supported. On average, obese people have a greater energy expenditure than their thin counterparts due to the energy required to maintain an increased body mass.
  Obesity is mostly preventable through a combination of social changes and personal choices. Changes to diet and exercising are the main treatments. Diet quality can be improved by reducing the consumption of energy-dense foods, such as those high in fat and sugars, and by increasing the intake of dietary fiber. Medications may be taken, along with a suitable diet, to reduce appetite or decrease fat absorption. If diet, exercise, and medication are not effective, a gastric balloon or surgery may be performed to reduce stomach volume or bowel length, leading to feeling full earlier or a reduced ability to absorb nutrients from food.
  Obesity is a leading preventable cause of death worldwide, with increasing rates in adults and children. In 2014, 600 million adults (13%) and 42 million children under the age of five were obese. Obesity is more common in women than men. Authorities view it as one of the most serious public health problems of the 21st century. Obesity is stigmatized in much of the modern world (particularly in the Western world), though it was seen as a symbol of wealth and fertility at other times in history and still is in some parts of the world. In 2013, the American Medical Association classified obesity as a disease. Viral hepatitis is liver inflammation due to a viral infection. It may present in acute (recent infection, relatively rapid onset) or chronic forms.
  The most common causes of viral hepatitis are the five unrelated hepatotropic viruses Hepatitis A, Hepatitis B, Hepatitis C, Hepatitis D, and Hepatitis E. In addition to the nominal hepatitis viruses, other viruses that can also cause liver inflammation include Cytomegalovirus, EpsteinBarr virus, and Yellow fever. Up to 1997 there has been also 52 cases of Viral hepatitis caused by Herpes simplex virus.
  There is the opportunity to prevent or treat the most common types. Hepatitis A and hepatitis B can be prevented by vaccination. Effective treatments for hepatitis C are available but expensive.
  In 2013 about 1.5 million people died from viral hepatitis. Most deaths are due to hepatitis B and hepatitis C. East Asia is the region of the world most affected. An opportunistic infection is an infection caused by pathogens (bacteria, viruses, fungi, or protozoa) that take advantage of an opportunity not normally available, such as a host with a weakened immune system, an altered microbiota (such as a disrupted gut flora), or breached integumentary barriers. Many of these pathogens do not cause disease in a healthy host that has a normal immune system. However, a compromised immune system, a penetrating injury, or a lack of competition from normal commensals presents an opportunity for the pathogen to infect.
candidates: dentistry infection infectious disease pathology surgery
answer: infectious disease