Читать книгу Basic Virology - Martinez J. Hewlett - Страница 70

Most virus‐induced diseases have low or only moderate mortality rates. Obviously, if a virus's mortality rate is too high, infection will kill off all the hosts so rapidly that a potential pool of susceptible individuals is lost. Exceptions to this rule do occur, however. Introduction of viral disease into a virgin population (perhaps due to intrusion into a novel ecosystem) can lead to high mortality. Prime examples are the spread of smallpox in Europe during the Middle Ages, and the destruction of native populations in the Western Hemisphere by the introduction of measles during the era of European expansion. Another exception to the low‐mortality rule comes about as a manifestation of infection with a virus that has an unusually long incubation period between the time of infection and the onset of symptoms of disease.