virus, as well as in people with known liver disease for whom hepatitis A infection could lead to liver failure. People in these groups who are not already immune can receive the hepatitis A vaccine. Those at high risk and in need of screening include: People with poor sanitary habits such as not washing hands after using the restroom or changing diapers People who do not have access to clean water People in close contact (either living with or having sexual contact) with someone who has hepatitis A People who use illicit drugs People with liver disease People traveling to an area with endemic hepatitis A The presence of anti-hepatitis A IgG in the blood indicates past infection with the virus or prior vaccination. Hepatitis B The CDC, WHO, USPSTF, and ACOG recommend routine hepatitis B screening for certain high-risk populations. Specifically, these populations include people who are: Born in countries where the prevalence of hepatitis B is high (defined as ≥2% of the population), whether or not they have been vaccinated Born in the United States whose parents are from countries where the prevalence of hepatitis B is very high (defined as ≥8% of the population), and who were not vaccinated HIV positive Intravenous drug users Men who have sex with men In close contact with (i.e. live or have sex with) people known to have hepatitis B Pregnant Beginning immunosuppressive or cytotoxic therapy Found to have elevated liver enzymes without a known cause Blood, organ, or tissue donors Incarcerated On hemodialysis Screening consists of a blood test that detects hepatitis B surface antigen (HBsAg). If HBsAg is present, a second test – usually done on the same blood sample – that detects the antibody for the hepatitis B core antigen (anti-HBcAg) can differentiate between acute and chronic infection. People who are high-risk whose blood tests negative for HBsAg can receive the hepatitis B vaccine to prevent future infection. Hepatitis C The CDC, WHO, USPSTF, AASLD, and ACOG recommend screening people at high risk for hepatitis C infection. These populations include people who are: Intravenous drug users (past or current) Intranasal illicit drug users HIV-positive Men who have sex with men Incarcerated, or who have been in the past On long-term hemodialysis, or who have been in the past Recipients of tattoos in an "unregulated setting" Recipients of blood products or organs prior to 1992 in the United States