Walsh & Hoyt: Virus-Host Interactions

The first step in the process of virushost interaction is exposure of a susceptible host to an infectious virus under conditions that are conducive to transmission. The infecting virus may be present in respiratory droplets or aerosols, in fecally contaminated food or water, in a body fluid or tissue such as blood, urine, saliva, cerebrospinal fluid (CSF), or in a transplanted organ to which the susceptible host is exposed. In some cases, the virus is inoculated directly into the host through the bite or scratch of an insect or animal vector or through the use of a contaminated instrument.