Viruses and some bacteria have been identified over the years as being responsible for, or catalysts for, various cancers over the years, and the Department of Health and Human Services monitors them to alert indviduals of these "known carcinogens." (You've likely seen the signs posted at restaurants or gas stations.)
"The list identifies factors including chemicals, agents like viruses, X-rays and ultraviolet radiation, and divides them into two categories — known to be a human carcinogen, and reasonably anticipated to be a human carcinogen," according to the HHS.
According to the "14th Report on Carcinogens," five viruses — which have been linked to more than 20 different types of cancer — are now being added to the category of "known to be a human carcinogen."
The viruses include the Human immunodeficiency virus type 1 (HIV-1), Human T-cell lymphotropic virus type 1 (HTLV-1), Merkel cell polyomavirus (MCV), and two herpes viruses - Epstein-Barr virus (EBV) and Kaposi sarcoma-associated herpes virus (KSHV).
"Since there are no vaccines available for these five viruses, prevention strategies are even more critical," Linda Birnbaum, director of the National Institute of Environmental Health Sciences, told reporters.
The inclusion of these new agents brings the cumulative total up to 248 known carcinogens. A listing indicates a cancer hazard, but does not by itself imply the substance or virus will cause cancer, according to the National Institues of Health.
People with HIV have long been known to be at risk for various cancers including Kaposi's sarcoma, cervical cancer, and non-Hodgkin's lymphoma. In addition, California researchers proved in 2009 that having an HIV-weakened immune system can significantly boost risks for other cancers as well, particularly those linked with viral infections like hepatitis, human papillomavirus, and Epstein-Barr.
The new report is available at here.