Influenza B-associated Reye's syndrome: incidence in Michigan and potential for prevention.

Prospective surveillance for Reye's syndrome in Michigan revealed the occurrence of 46 cases between December 15, 1973 and June 1, 1974. In an attempt to determine the incidence of influenza B-associated Reye's syndrome, a randomized point-prevalence survey of 1,041 schoolchildren was done in a county in Michigan where there had been simultaneous outbreaks of influenza B and Reye's syndrome. Of the children tested, 20% had titers of hemagglutination-inhibiting antibody to influenza virus B/Hong Kong/5/72 of greater than or equal 1:20. Based upon this countywide survey, the incidence of Reye's syndrome following influenza B was estimated as between 30.8 and 57.8 cases of Reye's syndrome per 100,000 cases of influenza B. A detailed epidemiologic investigation of the patients who developed Reye's syndrome indicated that the syndrome occurred four times more frequently in children living in rural areas than in children in the urban areas of the state. These studies indicate that, in addition to antecedent viral infections such as influenza B, factor(s) that are most likely extrinsic or environmental also play a role in the pathogenesis of Reye's syndrome.