Sources of infection among persons with acute hepatitis a and no identified risk factors during a sustained community-wide outbreak

Context. Hepatitis A is a common vaccine-preventable disease in the United States. Most cases occur during community-wide outbreaks, which can be diff icult to control. Many case-patients have no identified source. Objective. To identify foodborne and household sources of hepatitis A durin g a community-wide outbreak. Design. Serologic and descriptive survey. Setting. Salt Lake County, Utah. Participants. A total of 355 household contacts of 170 persons reported wit h hepatitis A during May 1996 to December 1996, who had no identified sourc e of infection; and 730 food handlers working in establishments where case- patients had eaten. Main Outcome Measure. Prevalence of immunoglobulin M antibodies to hepatiti s A virus (IgM anti-HAV) among household and food service contacts. Results. Overall, 70 household contacts (20%) were IgM anti-HAV-positive, i ncluding 52% of children 3 to 5 years old and 30% of children <3 years old. In multivariate analysis, the presence of a child <3 years old (odds ratio [OR]: 8.8; 95% confidence limit [CL]: 2.1,36) and a delay of greater than or equal to 14 days between illness onset and reporting (OR: 7.9; 95% CL: 1 .7,38) were associated with household transmission. Of 18 clusters of infec tions linked by transmission between households, 13 (72%) involved unrecogn ized infection among children <6 years old. No food handlers were IgM anti- HAV-positive. Conclusion. During a community-wide outbreak, HAV infection among children was common, was frequently unrecognized, and may have been an important sou rce of transmission within and between households. Transmission from commer cial food establishments was uncommon. Ongoing vaccination of children may prevent future outbreaks.