Acute hemorrhagic conjunctivitis caused by enterovirus type 70: an epidemic in American Samoa

From December 1981 to February 1982, an estimated 22,000 cases of acute hemorrhagic conjunctivitis (AHC) caused by enterovirus type 70 (EV 70) occurred among Samoan and non-Samoan residents of American Samoa. The overall attack rate was estimated to be 68%. Samoans of all ages resident in traditional housing and of large family size were at greatest risk of acquiring AHC, while non-Samoan adults resident in western style housing were at lowest risk. Epidemiologic aspects of AHC acquisition were also different for the Samoan and non-Samoan communities; index cases in Samoan households were frequently young adults, whereas index cases in non-Samoan households were commonly school age children, suggesting a role for school transmission in non-Samoans only. In this outbreak, subclinical AHC was rare; of 50 asymptomatic members of affected households, only 3 had neutralizing antibody to EV 70 (all with titers of 1:10). Investigation documented the highly contagious nature of AHC caused by EV 70, and the ease with which epidemic transmission may develop under conditions of crowding and frequent interpersonal contact.