ABSTRACT
The viral encephalitis epidemic during 2000 involved all the seven districts of Upper Assam (with 96.4% cases). The epidemiological, serological, clinical and entomological observations of the epidemic confirmed it to be due to JE. These were analysed, presented and discussed in the light of past history/records of the disease in the state. The epidemic was confined to the peak monsoon months of July and August (96% of the cases in the past). Serologically, 75-90% cases were confirmed to be due to JE. Case fatality Rate was 42.11% (overall average of the state in the past). There was no difference in case incidence among children or adults. Male to female ratio was 1:0.6. Based on the abundance and host preferences during the transmission period as well as virus isolation studies (as per past studies in the area) the main vectors Culex vishnui and Mansonia annulifera were susceptible to 4% DDT.