RESUMEN
Epidemic of Japanese Encephalitis has occurred in Andhra Pradesh during October-November, 1999 affecting 15 out of 23 districts. In total, 873 cases with 178 deaths have been recorded up to the day 29.11.99. The epidemiological investigation has been done in Anantapur district in western Andhra Pradesh, where the outbreak has started in the third week of October. In the district 47 PHC have been affected. On an average 4.5 per cent of 3175 villages have been affected. Average number of cases per affected village have been 1.5. Rural population has been primarily affected. Age groups 1-14 years including infants have been affected but nearly 86.8% of cases have been among 1-9 year age group. The overall case fatality rate has been 18.4 per cent. Clinical features have been high fever, headache, altered sensorium, convulsions and coma. A marked seasonal onset of a few cases per village and 93.75 per cent of human serum samples collected from hospitalised cases showed the evidence of J.E. virus infection indicating that the present outbreak was due to JE virus. High density of Culex vishnui complex mosquitoes has been observed in the area. All the environmental and ecological conditions, temperature, rainfall and relative humidity have been in favour of JE transmission. Analysis of the data for the last 10 years showed that the human JE cases occurred in Anantapur in September-October months, which shifted to October-November, 99. Prolonged draught conditions were observed till October. Possibly the delayed monsoon and congenial atmospheric conditions after monsoon were favourable to the vector species for extra-human cycle of transmission in 1999. Low level transmission leading to small number of cases continued during the succeeding years every September-October till the present epidemic. In all 24 PHCs and urban towns were identified with 212 cases and 39 deaths till 29.11.99.