A nationwide outbreak of Reye's Syndrome. Its epidemiologic relationship of influenza B

Between December 15 and June 30, 1974, 379 cases of confirmed Reye's syndrome were reported to the Center for Disease Control. Of these, 316 occurred during February and March 1974. A simultaneous surveillance system for influenza B indicated that this clustering of cases of Reye's syndrome correlated both temporally and geographically with influenza B outbreaks. The incidence of Reye's syndrome was higher in rural than in urban centers. Epidemiologically, two groups of cases of Reye's syndrome emerge: those which occur in older children (median age 11 years), cluster in time and geographic region, and are associated with antecedent influenza B infection; and those which occur sporadically thoughout the year, are isolated in occurrence, occur in younger children (median age 6 years), and are associated with a wide variety of antecedent viral illnesses.