Bacteria, viruses and parasites cause around 2m cases of cancer in the world each year, experts believe. 
 
 Of the 7.5m global deaths from cancer in 2008, an estimated 1.5m may have been due to potentially preventable or treatable infections. 
 
 Scientists carried out a statistical analysis of cancer incidence to calculate that around 16% of all cancers diagnosed in 2008 were infection-related. The proportion of cancers linked to infection was three times higher in developing countries than in developed ones. 
 
 Key cancer-causing infectious agents include human papillomavirus (HPV), the gastric bug Helicobacter pylori and the hepatitis B (HBV) and C viruses. 
 
 These four were together believed to be responsible for 1.9m cases of cancer, mostly gastric, liver and cervical cancers. 
 
 Cervical cancer accounted for around half of infection-related women's cancers. In men, more than 80% of infection-related cancers affected the liver, stomach and colon. 
 
 Dr Catherine de Martel and Dr Martyn Plummer, from the International Agency for Research on Cancer in Lyon, wrote in the Lancet Oncology journal: "Infections with certain viruses, bacteria, and parasites are one of the biggest and preventable causes of cancer worldwide … Application of existing public-health methods for infection prevention, such as vaccination, safer injection practice, or antimicrobial treatments, could have a substantial effect on future burden of cancer worldwide." 
 
 The researchers used information from a number of sources, including a cancer-incidence database covering 27 cancers from 184 countries. 
 
 Commenting on the findings, Dr Goodarz Danaei from the Harvard School of Public Medicine in Boston, wrote: "Their estimates show the potential for preventive and therapeutic programmes in less developed countries to significantly reduce the global burden of cancer and the vast disparities across regions and countries. 
 
 "Since effective and relatively low-cost vaccines for HPV and HBV are available, increasing coverage should be a priority for health systems in high-burden countries." ||||| Roughly one in six cancers is caused by an infection, according to a global study highlighting the power of vaccines in cancer prevention. 
 
 French researchers pooled data on 27 cancers from 184 countries to calculate the fraction of cases attributable to viral, bacterial and parasitic infections. 
 
 "Around 2 million cancer cases each year are caused by infectious agents," the researchers wrote in their report, published today in The Lancet Oncology. "Application of existing public health methods for infection prevention, such as vaccination, safer injection practice, or antimicrobial treatments, could have a substantial effect on the future burden of cancer worldwide." 
 
 Human papillomavirus (HPV), hepatitis B and C, and the ulcer inducing Helicobacter pylori caused 1.9 million cancers worldwide in 2008, according to the study. HPV and hepatitis B infections are largely preventable through vaccination, and H. pylori can be treated with antibiotics. 
 
 "Most of the infection-attributable cases occurred in less developed countries and were due to preventable or treatable infections," Goodarz Danaei, assistant professor of global health at the Harvard School of Public Health in Boston, wrote in an editorial accompanying the study. "Since effective and relatively low-cost vaccines for HPV and [hepatitis B] are available, increasing vaccine coverage should be a priority for health systems in high-burden countries." 
 
 HPV is a sexually transmitted infection that causes cervical cancer as well as cancers of the throat, vagina, vulva, anus and penis, according to the U.S. Centers for Disease Control and Prevention. The CDC recommends the HPV vaccine for teenage girls and boys as well as some men and women up to age 26, but few end up getting all the necessary doses. 
 
 "Our vaccination program is gaining momentum but very slowly, and one reason is it's hard to get teenagers in for all three doses," said Dr. William Schaffner, chair of preventive medicine at Vanderbilt University Medical Center in Nashville, Tenn. "The other reason is that because HPV is sexually transmitted, it's evoked a whole bunch of hullaballoo over whether the vaccine promotes promiscuity. Of course, there's no evidence to support that at all." 
 
 The hepatitis B vaccine is also given in three doses, but in the first 18 months of life. 
 
 "We vaccinate all children against hepatitis B, so their risk of liver cancer down the road will be very much reduced," said Schaffner. "If we look back 20 years from now, we will see the occurrence of liver cancer dropping precipitously." 
 
 The realization that infections like HPV can trigger cancer is relatively new, earning virologists Harald zur Hausen, Françoise Barré-Sinoussi and Luc Montagnier the Nobel Prize in 2008. 
 
 "Every time we make and advance like that, the opportunity exists to make a vaccine that could prevent those kinds of infections and thus prevent another proportion of cancers that occur in our population," said Schaffner. 
 
 But, he added, choosing not to smoke, eating a healthy diet and keeping physically active also reduce the risk of cancer. 
 
 "We have to remember that in our country behavioral risk factors still loom large," he said. "There are a number of strategies we can all employ to reduce our risk of cancer even more."
– A sixth of all cancers worldwide are the result of potentially treatable or preventable infections caused by bacteria, viruses, and parasites, according to a new study. Researchers found that that almost 2 million new cancer cases in 2008 were caused by the human papilloma virus, hepatitis B, hepatitis C, and the stomach bacterium Helicobacter pylori, and that the proportion of cancers caused by infection was three times higher in developing countries, reports the Guardian. A fifth of the 7.5 million cancer deaths worldwide in 2008 were caused by infection-related cancers, the study found. The research shows that vaccines for HPV and hepatitis B should be a priority for health care systems, notes an editorial accompanying the Lancet study. The HPV vaccination program is gaining momentum, but only very slowly, because "it’s hard to get teenagers in for all three doses," and "because HPV is sexually transmitted, it’s evoked a whole bunch of hullaballoo over whether the vaccine promotes promiscuity," the chair of preventive medicine at Vanderbilt University Medical Center tells ABC. Greater progress has been made with the hepatitis B vaccination program, he says, so the occurrence of liver cancer should be "dropping precipitously" over the next 20 years.