Background: Uncertainty exists about the current risk of hepatitis A virus infection in nonimmune travelers to destinations with high or intermediate risk of transmission. We analyzed recent epidemiological data on imported hepatitis A to determine region-specific attack rates and incidences.
Methods: Surveillance data on hepatitis A virus infections diagnosed during 1988-2004 were evaluated on the basis of notification by laboratories, additional reports of physicians, and traveler's statistics. This study focuses on international travelers with hepatitis A virus infection detected after their return to Switzerland.
Results: The rate of imported hepatitis A virus infections decreased 75% from 1988 to 2004 and accounted overall for 42% of all hepatitis A cases reported in Switzerland. The actual incidence of hepatitis A in travelers to countries of high or intermediate risk of transmission was 3.0-11.0 per 100,000 person-months abroad for all travelers and 6.0-28.0 per 100,000 for those presumed to be nonimmune. The actual proportion of those visiting friends and relatives among patients with hepatitis A has increased to 28.2%, with children aged 0-14 years predominating. Reductions in the incidence by hepatitis A vaccination were estimated to vary between 35.0% and 61.8% for different destinations.
Conclusions: The risk of hepatitis A virus infections has decreased by a factor of 10-50-fold over time, compared with findings from older studies. The risk, however, remains very considerable at many destinations, including frequently visited places, such as Mexico. Children of immigrants are a high-risk population. Strategies are needed to reach those at highest risk.