[The virological, epidemiological and clinical features of influenza A, B and C viruses]

Influenza epidemics that start abruptly and spread rapidly are caused by either influenza A or B virus. Although well-defined outbreaks of influenza C have rarely been reported, influenza C virus has been shown to cause a mild upper respiratory illness in children as well as in adults. Influenza A virus naturally infects several mammalian species including humans as well as a variety of avian species, whereas influenza B virus infects only humans. Influenza C virus primarily infects humans but has also been isolated from pigs. Furthermore, there are several differences in the biological and biochemical properties among three types of influenza virus. Here we summarize the virological, epidemiological and clinical features of influenza A, B and C viruses.