In the 11th Report on Carcinogens, the US government added Hepatitis C, Hepatitis B, and certain papilloma viruses to their list of substances known to be carcinogenic. This represented the first time ever that viruses were included.

At the sixth annual International Conference of the American Association for Cancer Research, Dr. Andrew J. Dannenberg stated, “I believe that, conservatively, 15 to 20% of all cancer is caused by infections, however, the number could be larger, maybe double.”

Dr. Dannenberg is director of the Cancer Center at New York-Presbyterian Hospital/Weill Cornell Medical Center. He went on to say, “Unfortunately, the public, as well as many health-care workers, are unaware of the significance of chronic infection as a potentially preventable cause of cancer.” Some examples he gave were liver cancer, caused by chronic Hepatitis B and C, and MALT lymphoma and adenocarcinoma of the stomach caused by Helicobacter pylori bacteria. Also, schistosome parasite infection has been implicated in bladder cancer (transitional cell carcinoma) .

Probably the most well known example is HPV, or human papilloma virus, known to cause genital warts and now known to be the major cause of cervical cancer. According to the National Cancer Institute, 11,000 women were diagnosed with cervical cancer in 2007, and nearly 4,000 of these would die from it. Oropharyngeal cancer is also thought to be caused, in some cases, by HPV infection and past HPV exposure.

The FDA approved Gardasil vaccination in 2006 to prevent infection against high-risk HPV’s known to cause cervical cancers and genital warts. Gardasil is approved for use in girls only, and can be given as young as nine years of age. This has led to some questions as to why the vaccine is not offered to boys if it is known that HPV causes oropharyngeal cancer as well as vaginal cancer. This may be because the vaccine is expensive and oropharyngeal is rare in comparison to cervical cancer.

What does the future hold for virus research? Likely much more research will be done to attempt to identify which viruses are associated with certain types of cancer. If this can be accomplished, perhaps the key to fighting cancer in the future will be to prevent people from getting cancer in the first place. If scientists can create a vaccine like Gardasil to prevent cervical cancer, it is not out of the realm of possibility to hope that some day they will come up with a vaccine for all cancers. One can always hope.

Reference

Report on Carcinogens, Eleventh Edition; U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program.

Further Reading

Human Papillomaviruses and Cancer: Questions and Answers; National Cancer Institute, US National Institutes of Health.