Even though human oncogenic viruses belong to different virus families and utilize diverse strategies to contribute to cancer development, they share many common features. One key feature is their ability to infect, but not kill, their host cell. In contrast to many other viruses that cause disease, oncogenic viruses have the tendency to establish long-term persistent in- fections. Consequently, they have evolved strategies for evading the host immune response, which would otherwise clear the virus during these persistent infections. Despite the viral eti- ology of several cancers, it appears that the viruses often may contribute to, but are not sufficient for, carcinogenesis; in fact, the majority of tumor virus-infected individuals do.
