The U.S. Department of Health and Human Services (HHS) added seven new substances to the 14th release of its Report on Carcinogens in November 2016. This brings the total number of HHS-identified carcinogens to 248.

Of the seven substances, five are viruses, one is a chemical, and one is a metallic element (see Table 1). The viruses are of particular note for a few reasons. First, the five viruses collectively are linked to more than 20 different types of cancers. Second, viruses have a fairly straightforward prevention strategy if vaccines can be developed to protect against them. Supporting research into identifying vaccines for these viruses could go a long way to reducing the world’s cancer burden in the future.

In a press release about the report, the National Institutes of Health voiced this caveat: “It’s important to note that a listing in the report indicates a cancer hazard but does not by itself mean that a substance or a virus will cause cancer. Many factors, including an individual’s susceptibility to a substance, and the amount and duration of exposure, can affect whether a person will develop cancer. In the case of viruses, a weakened immune system may also be a contributing factor. People should talk to their healthcare providers about decreasing their cancer risk from viruses.” 

Table 1. New Substances in the 14th Report on Carcinogens

Substance Listing Status Description
Human immunodeficiency virus type 1 (HIV-1) Known to be a human carcinogen Virus  
Human T-cell lymphotropic virus type 1 (HTLV-1) Known to be a human carcinogen Virus
Epstein-Barr virus (EBV) Known to be a human carcinogen Virus
Kaposi sarcoma-associated herpesvirus (KSHV) Known to be a human carcinogen Virus
Merkel cell polyomavirus (MCV) Known to be a human carcinogen Virus
Trichloroethylene (TCE) Known to be a human carcinogen Chemical (industrial solvent)
Cobalt and cobalt compounds that release cobalt ions in vivo Reasonably anticipated to be a human carcinogen A metal and its compounds