The short answer is no; humans cannot catch cancer. However, human beings can catch transmissible diseases that increase the risk of cancer.
Viruses
There are many viruses that cause diseases known to contribute to cancer risk. For example, human papillomavirus, or HPV, can cause cervical and other types of cancers by integrating its genome into the genome of the individual that it has infected. This can stop genes from being able to produce proteins that prevent cancer. Another cancer, Kaposi’s sarcoma, can be caused by the combined effects of two viruses. These are human immunodeficiency virus and human herpesvirus-8. Human herpesvirus-8, also known as HHV-8, causes cancer in the same way that HPV does. Individuals who are infected with human immunodeficiency virus, or HIV, have weakened immune systems. This means that individuals with HIV and HHV-8 have a significantly higher chance of being diagnosed with Kaposi’s sarcoma than those with just an HHV-8 infection.
Bacteria
Though bacteria do not integrate their genomes into the genomes of their hosts, they can also be cancer-causing. One prime example of this is the effect that an infection with the bacterium H. pylori has on cancer risk. Though about two-thirds of the global population have been infected with it, researchers have accepted that it is a cause of some gastric cancers. This may be because it increases inflammation in the stomach.
Can Animals Catch Cancer?
Though there is a risk of being infected with cancer-causing viruses, humans do not have to worry about catching cancer itself. The same can not be said for animals. One type of cancer, Sticker’s sarcoma, is known to spread between dogs. The tumor cells are passed from canine to canine by biting, licking, or even sex. The cancer most likely developed hundreds of years ago in a domesticated dog species that originated in Asia.
