California arbovirus (La Crosse) infections. I. Clinical and laboratory findings in 66 children with meningoencephalitis

California encephalitis (CE) is a significant cause of morbidity in Minnesota, accounting for 6.4% of all laboratory over a 5 yr period. CE occurred in 66 children aged 6 mth to 17 yr. All patients were from rural or suburban areas. A mild and a severe clinical form of CE were defined, with the severe form becoming more prevalent during the last 2 years. Focal neurologic findings were present in 16% of patients and localized abnormalities were seen in 40% of EEGs and brain scans. All patients survived but 15% had sequelae. Comparative neutralization and immunodiffusion tests indicated that La Crosse was the subtype responsible for CE in all patients appropriately studied. Since the diagnosis of CE depends on serology, antibody responses in patients during the acute illness and for 2 yr thereafter are described. The clinical features of CE are contrasted with those of herpesvirus, mumps, and enteroviral meningoencephalitis.