The duration of viremia and time course for development of IgM antibodies were determined prospectively in natural and experimental hepatitis A virus (HAV) infection. Serial serum samples from HAV-infected men (n=13) and experimentally infected chimpanzees (n=5) were examined by nested reverse-transcriptase polymerase chain reaction analysis to detect HAV RNA and by ELISA to detect IgM antibodies to HAV. Among infected humans, HAV RNA was detected an average of 17 days before the alanine aminotransferase peak, and viremia persisted for an average of 79 days after the liver enzyme peak. The average duration of viremia was 95 days (range, 36-391 days). Results were similar in chimpanzees. In addition, HAV RNA was detected in serum of humans and chimpanzees several days before IgM antibodies to HAV were detected. These results indicate that adults with HAV infection are viremic for as long as 30 days before the onset of symptoms and that the duration of viremia may be longer than previously described.

HAV is often transmitted within networks of persons with similar risk factors, which may be the infection source for others in the community.

In 1993-94, a community-wide outbreak of hepatitis A occurred in Stanislaus County, California. Stool specimens collected from a sample of 33 case patients were used to evaluate the duration of hepatitis A virus (HAV) excretion and the genetic relatedness of HAV isolates. Twenty-four percent of the patients had a stool sample positive for HAV antigen by enzyme immunoassay, whereas 91% had at least one stool positive for HAV RNA by RT-PCR amplification. Children were found to excrete low levels of HAV RNA for up to 10 weeks after the onset of symptoms. Analysis of the HAV VP1 amino terminus and VP1/P2A regions showed that a limited number of HAV isolates circulated during the epidemic and the majority of the cases were infected with the same strain.