Type A Viral Hepatitis

IN recent years, our understanding of the nature and diversity of viruses causing hepatitis in human beings has been sharply increased.1 Those agents now include the viruses of hepatitis A (classic short-incubation infectious hepatitis) and hepatitis B (long-incubation serum hepatitis), one or more still-undefined viruses responsible for "non-A,non-B hepatitis," and the recently recognized delta virus. Among these types of hepatitis, each of which occurs commonly within the United States, hepatitis A is uniquely and primarily transmitted by the fecal—oral route and thus possesses an unequaled potential for epidemic spread. Although it is relatively benign and never eventuates in chronic hepatitis, . . .