Ten patients with acute encephalopathy or encephalitis associated with influenza-like illness, admitted to hospitals in Nagoya, Japan, during 12 months, 1996-97, mainly mid-winter, had cerebrospinal fluid examined by PCR for influenza A and B. Seven patients, aged 2 to 4 years, had generalized convulsions within 2 days of fever onset and evidence of recent influenza infection, type-A/Hong Kong (H3N2) in 6 and type B in 1. PCR for influenza A was positive in the csf of 5 patients. Two died, one had sequelae, and 4 recovered without complications. One child had clinical features similar to Reye’s syndrome. 
COMMENT. An outbreak of influenza-associated encephalopathy or encephalitis in the winter of 1996-97 in Nagoya, Japan, was mainly due to type A. Direct viral involvement of the central nervous system was confirmed by positive PCR results in the cerebrospinal fluid. The clinical profiles of this outbreak were different from most previous epidemics.
Viral encephalitis, especially influenza, during pregnancy and early childhood is a potential and possibly overlooked factor in the cause of the ADHD syndrome.