Hepatitis A is a common vaccine-preventable disease in Mongolia. Most cases occurred during a community-wide outbreak that was difficult to control. The 2007 annual incidence of 34 cases per 10,000 population was 8 times higher than the national average rate.
Objective To describe the distribution of cases and clinical manifestations, and to identify sources of infection of hepatitis A among children living in communities with the highest rates of infection during the community-wide outbreak.
Design Serologic and descriptive survey.
Participants Between September and December 2007, 405 schoolchildren, 353 kindergarten children and 128 children cared for at home were hospitalized for hepatitis A.
Main outcome measure Incidence of immunoglobulin M antibodies to hepatitis A virus and clinical criteria of case definition among hospitalized children at the National Center of Infectious Diseases.
Results Most Mongolian cases of hepatitis A occurred during a community-wide outbreak. 19% of cases lived in a household where a previous case occurred. IgM anti-HAV positive cases where skewed toward the younger age group, with 34%, 39%, 13%, and 24% among 2–4 years, 5–9 years, 10–14 years, and greater than 15 years, respectively. Given that more than 70% of cases are asymptomatic in young children, it is estimated that over 2000 cases occurred related to the outbreak.
Conclusion During a community-wide outbreak, HAV infection among children was common, frequently unrecognized, and may have been an important source of transmission within and between kindergarten, school and households. Ongoing vaccination of children may prevent future outbreaks.