According to the American Cancer Society, several viruses have been linked to cancer in humans. Viruses work by entering living cells and hijacking their machinery in order to reproduce and make more viruses. To do so, the ACS notes that many viruses will insert their own DNA or RNA into their host cells, affecting those cells’ genes. That can push the cell toward becoming cancer. At least a dozen types of human papillomaviruses, or HPVs, are known to cause cancer. That’s important to note, as the ACS says most sexually active people are infected with one or more of the more than 40 types of HPVs that are passed on through sexual contact. In addition to HPVs, a type of herpes virus known as the Epstein-Barr virus as well as HIV and hepatitis B and C have also been found to cause cancer. It’s equally important to point out that while these and other viruses can cause cancer, that does not mean everyone who has been diagnosed with them will get cancer. But people who have been diagnosed with cancer-causing viruses should discuss their cancer risk with their physicians, making sure to ask if there is anything they can do to lower their risk for the disease.