Poliomyelitis outbreak in Israel, 1950-1.

The epidemicity of poliomyelitis in Israel since 1950 is reviewed, and the influence of the mass immigration which took place between 1948 and 1952 is discussed. Age distribution and attack-rates among Arabs, among Jewish population-groups originating in different countries, and among old residents and new immigrants, are examined. It is suggested that the change from endemicity to epidemicity of the disease may have been due to general overcrowding during the pre-epidemic period, and to enhanced circulation of virus (type 1), and a resulting increase in its pathogenicity.