Retrovirus Survival: The Human Threat

Abstract The SHV story shows how a retrovirus can change and spread in new species, causing disease when it was previously harmless. The story also shows that a retrovirus generally stays in its natural host species, causing little or no harm, as long as that species is widely available. As long as talapoin monkeys stay in the western equatorial rain forest, for example, SRV appears not to infect other susceptible species nearby. It enters such hosts only rarely and with insufficient persistence to establish itself. SRV and its talapoin host are mutually adapted. Retroviral movement appears to be largely a function of environmental instability since the main force for retrovirus survival is adaptation to environmental change. Such change may concern the microenvironment of a single host or the macrocnvironment of the host community, or a combination of both. The process seems to start at the macro level, where the main factor is the availability of susceptible hosts. After all, if an accustomed host is decimated, a virus dies with the host unless it happens to gain a foothold in a new species. The new host must be susceptible and close at hand, especially if close contact is needed for transmission.