The pathologic effects of viral diseases result from (a) toxic effect of viral genes products on the metabolism of infected cells, (b) reactions of the host to infected cells expressing virus genes, and (c) modifications of cellular functions by the interaction of cellular DNA or proteins with viral gene products (see chapter 44.) In many instances, the symptoms and signs of acute viral diseases can be directly related to the destruction of cells by the infecting virus. The keys to understanding how viruses multiply are a set of concepts and definitions.
To multiply, a virus must first infect a cell. Susceptibility defines the capacity of a cell or animal to become infected. The host range of a virus defines both the kinds of tissue cells and the animal species which it can infect and in which it can multiply. Viruses differ considerably with respect to their host range. Some viruses (e.g. St. Louis encephalitis) have a wide host range whereas the host range of others (e.g. human papillomaviruses) may be a specific set of differentiated cells of one species (e.g human keratinocytes). Determinants of the host range and susceptibility are discussed in the next section.
Copyright © 1996, The University of Texas Medical Branch at Galveston.