An estimate of the incidence of hepatitis A in unimmunized Canadian travelers to developing countries.

Abstract

There is a paucity of data describing the risk of acquiring hepatitis A while traveling in the developing world. This paper uses available data to calculate the risk to Canadian travelers. Information was gathered from Canadian and international sources on the following: the yearly incidence of hepatitis A among Canadians; the proportion of cases of hepatitis A associated with travel to developing countries; the number of days of such travel by Canadians per year; and the percentage of travelers immunized before departure. Calculations were performed on these figures to arrive at an estimated risk of infection for unimmunized Canadian travelers. The annual incidence of hepatitis A in Canada over the period 1996-2001, adjusted for underreporting, averaged 6.15 cases/100,000 people. During that time, Canadians traveled approximately 36.5 million days/year in developing countries. The literature shows that 4% to 28% (mean 16%) of cases are estimated to have been acquired abroad. It also shows that 14% to 24% (mean 19%) of such travelers are immunized before departure. Based on these figures, the risk of acquiring hepatitis A during 1 month of travel in the developing world is calculated to be approximately 1 case per 3,000 unimmunized travelers. Hepatitis A is an important travel-related disease, preventable by immunization. However, our calculations indicate that the risk of acquiring hepatitis A while traveling in the developing world is lower than some previously published estimates. The results represent an average for all types of travel to all such countries. The actual risk will vary considerably, depending on the destination and style of travel.