The following information was developed by the American Cancer Society, and is presented on Cancer.Net as part of a collaboration between the American Society of Clinical Oncology (ASCO) and the American Cancer Society. Both organizations have long shared a commitment to empowering people with information about cancer they can trust. Learn more about this collaboration and how it will help advance that goal. Used with permission. © 2022.
Cancer is NOT contagious
You cannot “catch” cancer from someone else. Close contact or things like sex, kissing, touching, sharing meals, or breathing the same air cannot spread cancer. Cancer cells from someone with cancer are not able to live in the body of another healthy person. The immune system finds and destroys foreign cells, including cancer cells from another person.
Why cancer might appear to be contagious
Although cancer is not contagious, there are some situations that can make people think that cancer has spread from one person to another.
Infections that increase cancer risk
Although cancer itself is not contagious, there are some germs that can play a role in the development of certain types of cancer. This may lead some people to wrongly think that “cancer is catching.” Infections that have been linked to cancer include viruses, bacteria and parasites.
Cancer in families
If cancer were contagious, we would have cancer outbreaks just as we do with the flu. We would expect a high rate of cancer among the families and friends of people with cancer and among health professionals who care for them. This is not the case.
The fact that cancer might happen more often in certain families does not mean that the family members have spread cancer to each other. Reasons for this include:
Family members share the same genes.
Families may have similar unhealthy lifestyles (diet and smoking, for example).
Family members might all be exposed to the same cancer-causing agent.
Some people point to “clusters” of cancer patients who have had contact with each other as proof that cancer is contagious. But clusters almost never reflect a higher rate of cancer than in the general public. In rare cases where there is more cancer in a group, it’s hard to know what other factors, such as exposure to cancer-causing agents and lifestyle, might be responsible for the cancer cluster.
Cancer transfer during organ transplant
In very rare cases, cancer cells from an organ donor have caused cancer to grow in the person who got the organ. This does not happen often, because our immune systems look for cells that are not our own and destroys them. However, people who get organ transplants must take medicines to weaken their immune systems so their body doesn't attack and destroy the transplanted organ. Organ donors are carefully screened for cancer to reduce this risk.
Still, recent studies have shown that cancer is more common in people who get organ transplants. This is likely because of the drugs given to reduce the risk of organ rejection, rather than cancer spreading from the donated organ. Because these drugs weaken the immune system, they can prevent the body from finding and attacking damaged cells and viruses that can lead to cancer.
Cancer transfer during pregnancy
Even if a woman has cancer during pregnancy, the cancer rarely affects the baby. Some cancers can spread from the mother to the placenta (the organ that connects the mother to the baby), but most cancers cannot affect the baby itself.
People with cancer need to be around other people
Even today, families, friends, and co-workers will sometimes stay away from a loved one with cancer. This can make the person with cancer feel isolated and alone. But you cannot “catch” cancer from them. Don’t be afraid reach out to the person with cancer. They need your visits and support.
This information was originally published at https://www.cancer.org/cancer/cancer-causes/is-cancer-contagious.html.
© 2022 American Cancer Society. All rights reserved worldwide.