Improved surveillance of Japanese encephalitis by detection of virus-specific IgM in desiccated blood specimens.

An IgM antibody-capture type enzyme-linked immunoassay (MAC ELISA) was compared with the haemagglutination inhibition method (HI) for establishing a laboratory diagnosis of acute Japanese encephalitis (JE) virus infection using specimens of dried blood eluted from filter paper strips. Paired samples from 243 encephalitis patients, which had been obtained by mail through a national surveillance programme in Thailand, were tested. During the peak of the 1983 encephalitis epidemic, 72% of cases were diagnosed as Japanese encephalitis by MAC ELISA, compared with only 38% by HI. During non-epidemic periods, the proportions diagnosed as Japanese encephalitis by MAC ELISA or HI were 26% and 33%, respectively. Detection of IgM anti-JE activity by the antibody-capture immunoassay is superior to the HI method for establishing a diagnosis of acute Japanese encephalitis using dried blood specimens.