This question is often asked by cancer patients or their families, and for many years, medical doctors believed that human cancers were not contagious. Some viral infections associated with the development of cancer (human papillomavirus, hepatitis B virus, EBV, etc.) have been linked to the development of cervical cancer, liver cancer, nasopharyngeal cancer and lymphoma, but so far there has been no evidence that these cancers can be transmitted directly to others. The incidence of cancer among medical personnel engaged in the diagnosis and treatment of tumors has also not been seen to be higher than that of the population in other jobs. Epidemiologic investigations have found that certain cancers are associated with insect transmission. For example, African children with Burkitt’s lymphoma have a high prevalence of EBV infection, and the distribution of tumors is consistent with malaria-endemic areas, with mosquitoes presumed to act as vectors for both diseases. Viral antigens or antibodies can be found in some cancer patients. For example, herpes simplex virus type B can be detected in 80% of patients with cervical cancer, and antibodies to EBV can be detected in 70% to 90% of patients with nasopharyngeal carcinoma. All of the above examples show that there is a very close relationship between the occurrence of cancer and viral infections, but there is a lack of sufficient evidence to show that these cancers are directly transmitted by viral infections. Recent studies have shown that there are not many types of oncogenic viruses associated with human tumors. Due to the different types of viruses, they integrate into the genome (DNA sequence) of human cells through the mechanism of viral RNA transduction or insertion, or through the integration of viral DNA into the genome of human cells, which leads to the activation of proto-oncogenes and/or inactivation of oncogenes, resulting in the transformation of the cells to sustained proliferation, and thus the formation of tumors.