Influenza Type B-Related Encephalopathy: The 1971 Outbreak of Reye Syndrome in Chicago

Between Jan 15 and March 15, 1971, forty-eight grade-school patients living in western Chicago were hospitalized with an encephalopathic illness. Fourteen of these children had illnesses compatible with Reye syndrome (encephalopathy with liver impairment). Most of the children showed evidence of central nervous system (CNS) dysfunction within ten days after onset of a febrile upper respiratory tract illness. Seizures developed in 11 of the 48 patients (including 4 of the 14 with Reye syndrome). Eight of the encephalopathic patients, including 6 of the 14 with Reye syndrome, died. Two children without Reye syndrome had abnormalities of liver enzymes coincident with cerebrospinal fluid pleocytosis. Sixteen of the 24 patients tested had titer rises in serum against influenza type B only; influenza type B was isolated from throat cultures of 2 patients. This, the seventh report of CNS complications (Reye syndrome) associated with influenza type B, suggests that surveillance for neurologic sequelae should become part of the epidemiologic evaluation of influenza epidemics.