Walsh & Hoyt: Virus-Environment Interactions

For a virus to propagate itself in nature, the outcome of a virushost interaction, regardless of the ultimate effect on the host, must be the shedding of more virus particles into the environment in a manner that optimizes the potential for the infection of subsequent susceptible hosts. As noted previously, viruses may be shed from an infected host in a variety of ways. They may be expelled from the respiratory tract in the form of aerosols generated by coughing or sneezing. They may be contained in saliva and transmitted through biting or intimate personal contact. Virus contained in feces or urine may contaminate food or water that is subsequently ingested. Virus in semen or genital secretions may be transmitted during sexual intercourse or other sexual activities. Each of these modes of transmission requires that the virus remain infectious under specifically defined environmental conditions, and they also provide clues to the inactivation of particular viruses.