Is Cancer Contagious? What the Science Says

Cancer itself is not contagious. You cannot catch cancer from another person, the way you catch a cold or the flu. Hugging, kissing, sharing food, or caring for someone with cancer will not give you cancer. But a few infections that spread between people are linked to a higher risk of certain cancers later on. That distinction matters. It is worth understanding clearly.

Some viruses, bacteria, and parasites raise the risk of specific cancers. These infections can spread from person to person. The cancer that sometimes follows, years later, does not spread that way at all. It is the infection that is transmissible. The cancer itself is not.

HPV (human papillomavirus) spreads through sexual contact. High-risk types of HPV cause nearly all cervical cancers. They also cause some cancers of the throat, anus, and genital area. HPV vaccination and screening tests can prevent many of these cancers.

Hepatitis B and hepatitis C spread through blood and certain body fluids. Long-term infection with either virus can lead to liver cancer over time. A vaccine exists for hepatitis B. Treatments exist for both viruses that can lower this risk.

Epstein-Barr virus (EBV) spreads mainly through saliva. It is linked to some lymphomas, and to nose and throat cancers.

H. pylori is a bacterium. It spreads through close contact, often within families. Over many years, it can cause stomach cancer and a type of stomach lymphoma.

HIV weakens the immune system. That weakening raises the risk of several other cancers. A healthy immune system normally helps control abnormal cells before they can grow into cancer.

Vaccines exist for HPV and hepatitis B. Getting vaccinated is one of the most effective ways to prevent the cancers linked to those viruses. Practicing safer sex, not sharing needles, and getting tested for hepatitis B and C all lower your chance of an infection that could raise cancer risk later. Routine screening, like Pap tests and HPV tests for cervical cancer, catches problems early. Often, this happens before cancer ever develops.

It is an understandable fear. Cancer is common and frightening. It sometimes clusters within families or communities, which can make it feel contagious even when it is not. Family clustering usually comes from shared genes, shared environment, or shared habits like smoking. It does not come from person-to-person spread of the cancer itself. If cancer runs in your family, that is worth discussing with your doctor. It is a genetic and environmental question, not a contagious one.

There is one rare, specific exception worth knowing about. In a small number of organ transplants, cancer cells from a donor's organ have been passed to the recipient, because the recipient's immune system is deliberately suppressed to prevent organ rejection. NCI puts that risk at about two cases of cancer per 10,000 organ transplants. This is not the same as catching cancer through ordinary contact. Transplant centers screen donors carefully for cancer history specifically because of this rare risk, and it does not apply to everyday life at all. Research also has not found that cancer can spread through a blood transfusion.

If someone in your home has cancer, you do not need to change how you interact with them out of fear of catching it. You can hug them, share meals, and use the same bathroom without any risk of getting their cancer. The one exception to be mindful of is during chemotherapy, when a person's own infection risk is high, so it is often them who needs protection from common germs, not the other way around.

Ask whether you have ever been tested for hepatitis B or C, especially if you have never been vaccinated for hepatitis B. Ask whether HPV vaccination makes sense for you or your children, and up to what age it is recommended. Ask about your own risk factors if a cancer-linked infection runs in your family or community.

• National Cancer Institute — Infectious Agents and Cancer Risk.
• American Cancer Society — Is Cancer Contagious?.
• National Cancer Institute — Common Cancer Myths and Misconceptions.