Influenza surveillance in Israel, 1976--77.

An influenza surveillance program developed and conducted in three districts in Israel during winter 1976--77, was based mainly on morbidity data in the general population, corroborated by sero-epidemiologic surveys on selected groups. This information was supplemented by data on mortality organized according to specific age groups. During the period under study, similar results were observed in each of the three districts surveyed. Two successive waves of influenza were recorded: an early wave due to B/Hong Kong/5/72 followed by an A/Victoria/3/75 outbreak. Both waves were of moderate extent, with the highest frequency of clinical influenza occurring in the youngest group, age 0--14 years. The age-specific mortality rates were highest and rather similar in the extreme age groups 65+ and 0. The search of A/New Jersey/8/76 antibody revealed a considerable proportion of positives with a higher titer in the older age groups. A special serologic survey among Yemenite Jews over 50 years of age, who immigrated to Israel in 1949, showed that the 1918 influenza pandemic also reached that isolated country. The surveillance program provided an early warning system as well as a rather accurate measurement of influenza impact in Israel.