The human body is colonized by billions of bacteria and bacteriophages, comprising hundreds of species and genera that make up our microbiome (Walker and Hoyles 2023). These bacteria and their phages inhabit us from birth as babies pass through the vaginal canal and begin to acquire organisms from their mothers. Nearly all domains of our bodies from our skin to our digestive system team with this invisible multitude. By definition, these commensal organisms that make up our microbiome are mostly innocuous while many even contribute to our health and normal bodily functions. While the exact composition of individual microbiomes can differ, certain types of bacteria are universally found in humans and likely have a symbiotic relationship with us. We provide a host environment for the bacteria to thrive in and they provide some benefit to us. In contrast, viruses were not historically considered part of our endogenous flora. Instead, viruses were perceived as purely exogenous pathogens that we transiently acquired. This was certainly true for many common disease-causing viruses like influenza (Chap. 5 ), polio (Chap. 6 ), or hepatitis A (Chap. 9 ). Not everyone had these viruses, and after an infection, the virus was cleared and did not remain associated with the recovered individual. Even the discovery of viruses like hepatitis B (Chap. 8 ) or chickenpox (Chap. 10 ) that can establish permanent infections didn’t change the basic paradigm. These viruses are still considered external pathogens found only in a subset of humans and are not considered part of the normal human microbiome. However, if any virus can be considered a commensal organism that is part of the normal human flora, it is the human papillomaviruses (HPVs). These viruses are the causative agents of papillomas (hence the name papillomaviruses), what we commonly call warts. More importantly than benign skin warts, HPVs are the major cause of cervical cancer and an important contributor to some forms of anal, oral, and skin cancers (Tornesello and Buonaguro 2020).