Epidemiologic features of Reye syndrome seen in southwestern Pennsylvania 1970-80.

In 11 years of surveillance in southwestern Pennsylvania there were 97 cases of Reye syndrome. Peak incidence was in February and March, corresponding to periods of influenza A and B activity. Mean age of cases was 7.9 years; 57 per cent were female. Case fatality declined from 55 per cent in 1970-75 to 16 per cent in 1976-80 (p less than .001). Influenza was associated with 45 per cent of cases, varicella 19 per cent; the remaining 36 per cent of cases did not occur during periods of influenza activity. Reye syndrome occurred significantly more frequently in suburban and rural areas than in central city (p less than .01), more frequently among White persons than Blacks (p less than .01), and more frequently in counties where the total population under 17 years was less than 25,000 (p less than .01).