SEROLOGICAL EVIDENCE FOR RECENT INFECTION WITH HEPATITIS-A VIRUS (HAV) FOLLOWING AN INSTITUTIONAL OUTBREAK OF HEPATITIS

An outbreak of infectious hepatitis in a college for nursery nurses was studied retrospectively by a newly available test for anti-HAV. Of the nine cases of infectious hepatitis six had anti-HAV (hepatitis A virus) specific IgM in sera collected 40 to 91 days after the onset of illness. Of the 63 people who were not ill, two were found to have specific IgM. Two adults with non-icteric illnesses during the outbreak had anti-HAV but no specific IgM. The overall serological results indicate that not more than 12 per cent of adults were immune at the beginning, and 33 per cent were immune at the end of the outbreak. The incidence of anti-HAV was higher in the groups closely exposed to the probable source of the outbreak, viz 100 per cent in the resident children, 64 per cent and 75 per cent in two sets of students, and 38 per cent in the nursery staff. It is likely that during the outbreak all the children were subclinically infected. By contrast sub-clinical infections were almost certainly less common than clinical infections in the adults. The test for antibody for HAV was useful in tracing the spread of the virus in the institution and, modified to detect specific IgM, could detect evidence of recent infection in a single serum collected up to three months after the onset of illness. © 1979 The British Society for the Study of Infection.