Читать книгу Basic Virology - Martinez J. Hewlett - Страница 44

Most (but certainly not all) virus infections induce an effective and lasting immune response. Some of the basic features of this response are described in Part II, Chapters 7 and 8. An effective immune response means that local outbreaks of infection result in the formation of a population of resistant hosts – often termed herd immunity. This means that any virus that induces protective immunity must maintain itself either in another reservoir or by dynamically spreading in “waves” through the population at large. If enough members of the susceptible population become immune, virus cannot spread effectively and it becomes extinct. This herd immunity is a major factor in both gradual and abrupt acquisition of genetic alterations that create new serotypes of viruses that can escape immunity to the original strain.