Hepatitis A virus antibodies in Belgium: relationship between prevalence and age.

Epidemiological data from various countries show that the frequency of Hepatitis A virus antibodies (anti-HAV) in different population groups is largely dependent on the geographical and age distribution of the population surveyed. As regards Europe anti-HAV antibodies are generally frequent in all groups in Southern Europe while in Northern Europe these antibodies are common in older people only. The prevalence data collected in 1979 and in 1989 show that the anti-HAV antibodies rate is a function of age, but the rates for all age groups were lower in 1989 compared to 1979. In 1979, at an age between 25 and 30, some 50% of the population was anti-HAV antibody positive. The same results were obtained in another Belgian study conducted in 1979. In 1989 50% positivity was only reached at an age between 35 and 40 years. The present study confirms that anti-HAV antibody prevalence decreases with higher socioeconomic status. The higher rate relative to age is associated with socioeconomic and hygienic living conditions at the time when most infections occur, i.e. before the age of 20. It can be concluded by comparing the 1979 and 1989 results that the number of adults susceptible to HAV infections has increased. This fact drew attention in view of the strongly altered travelling pattern of fairly large sections of the population.