Читать книгу Principles of Virology, Volume 2 - Jane Flint, S. Jane Flint - Страница 49

In contrast to cultured cells that grow under conditions of stable temperature and humidity, or laboratory animals that live in strictly controlled enclosures, humans and other animals exist in ever-changing environments that directly influence viral biology. These changes include normal seasonal variations as well as progressive changes, such as climate change.

Climate, including temperature and humidity, can have a profound influence on viral infections of populations. Indeed, there is a striking seasonal variation in the incidence of most acute viral diseases (Fig. 1.10). Respiratory virus infections occur more frequently in winter months, whereas infections of the gastrointestinal tract predominate in the summer. Seasonal differences in diseases caused by arthropod-borne viruses are clearly a consequence of the life cycle of the insect vector; when there are fewer mosquitos, there is a parallel reduction in the prevalence of the viruses that they harbor. However, the basis for the seasonal nature of infections by viruses that are not transmitted by arthropod vectors is less obvious. It has been suggested that the seasonality of some infections is attributable to temperature- or humidity-based differences in the stability of virus particles. For example, poliomyelitis was known as a summertime disease in New England; in Hawaii, however, with its stable and temperate climate, poliovirus infections occurred throughout the year. The prevailing view is that poliovirus is inactivated during winter months when humidity is low. In contrast, other viruses, such as influenza virus, remain infectious through the drier winter months.