Inapparent Infection with Western Equine Encephalitis Virus: Epidemiologic Observations

Abstract

Antibodies against western equine encephalitis (WEE) virus were demonstrated in 10.9% of 614 inhabitants of Weld County, Colorado, during 1954. The percentage of persons with WEE antibodies, who were under 30 years of age, was twice as high as for persons who were over 30 years of age. Males and females had similar rates when all age groups were totaled, but the percentage of positives was greater in males ages 15-30, greater in females ages 45 and over. Residents living in the County for 15-24 years had higher rates than newcomers to the area. No significant difference was noted in the frequency of inapparent infections in rural as compared with urban areas or in irrigated as compared with non-irrigated areas. Persons with outdoor employment had 4 times as many inapparent infections as those with indoor employment. None of 78 individuals bled again in the fall developed detectable neutralizing antibodies against WEE virus during the summer.