A few treatable infections lead to over 2 million cancers a year.

Human papillomavirus, hepatitis B, hepatitis C and the stomach bacterium Helicobacter pylori are the leading infections which can cause cancer as well as HIV.

Merck’s Gardasil vaccine is used to prevent the human papillomavirus ,which is responsible for cervical and some head and neck cancers, is available for both men and women.

The expectation is that eliminating the virus will help to end the cancers.

In terms of deaths, the study authors estimated that 1.5 million of the 7.5 million cancer deaths that occurred worldwide in 2008 – or about one in five – were related to infectious diseases.

How do researchers know if a cancer is caused by an infectious disease? Viruses such as HPV and Hepatitis B and C actually invade a person’s DNA and leave their signature in the genetic sequence. Helicobacter pylori does not, but the bacterium can be found in gastric tumors.