National surveillance for Reye syndrome: a five-year review.

National surveillance for Reye syndrome conducted during five years, including the period 1973-1974 and December 1976 through November 1980, has resulted in the reporting of more than 2,000 cases of Reye syndrome. The highest reported incidence of Reye syndrome occurred during years of primary influenza B and A (H1N1) activity; the reported incidence during one period of influenza A (H3N2) activity was somewhat lower. Regional outbreaks of Reye syndrome have been associated with influenza A (H1N1) and B but now with influenza A (H3N2). Cases of Reye syndrome in whites tend to be distributed throughout all age groups whereas a large percentage of cases in blacks have been reported in infants less than 1 year of age in three of the past four years. Nationally, there has been a decline in the case-fatality ratio in recent years.