Community Wide Outbreak of Acute Hepatitis A Virus in Mongolia, 2007

Hepatitis A is a common vaccine-preventable disease in the Mongolia. Most cases occur during community-wide outbreaks that can be difficult to control. The 2007 annual incidence of 34 cases per 10,000 population is 8 times higher than the national average rate.

Objective. To identify sources of infection of hepatitis A among children living in communities with the highest rates of infection during a community-wide outbreak.

Design. Serologic and descriptive survey.

Participants. A total of 405 schoolchildren, 353 kindergarten children and 128 household contacts with hepatitis A during September 2007 to December 2007.

Main Outcome Measure. Incidence of immunoglobulin M antibodies to hepatitis A virus (IgM anti-HAV) and clinical criteria of case definition among patients of National center of infectious diseases.

Results. Most Mongolian cases of hepatitis A result from person-to-person transmission during community wide outbreaks. The most frequently reported source of infection is either household (19%) or children living in communities (50%). IgM anti-HAV positive varies directly with age: among persons 2-4 years of age, the incidence is 34%; 5-9 years of age, 39%; 10-14 years of age, 13.4%; and greater than 15 years of age, 24%. The result of HAV infection that occurred months to years previously, 82% reported of HAV infection during September to December, 2007.

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.