The significance of anti-HAV in different population sectors in Lebanon: a comparative seroepidemiologic study.

A comparative seroepidemiologic survey was performed on the prevalence of antibody to HAV (anti-HAV) in 772 subjects in Lebanon. The results show that 97.7% of the adult Lebanese carry anti-HAV in their sera irrespective of geographic or socioeconomic factors, as compared to 38.8% of the adult foreign population. In the paediatric group, the highest prevalence of anti-HAV was encountered at the age of 1-120 days indicating placental transfer of maternal anti-HAV. In the 1-5 year age group there is a sharp drop of anti-HAV to 40%. The anti-HAV of this age group indicates a response to actual infection with HAV. At 12 years the prevalence of anti-HAV is 85%, approaching that of adults. This survey indicates that Lebanon is an endemic area for HAV infection. The age of onset of this infection may be as early as five months, is commonest in the 1-6 year age group and becomes rare again after the age of 12. Finally, fractionation of immunoglobulins of test sera demonstrated that all subjects had their anti-HAV activity in the IgG class, denoting either maternal transfer or old infection and acquired immunity.