JAPANESE ENCEPHALITIS SURVEILLANCE IN CHINA (PROVINCE OF TAIWAN) DURING 1968-1971

Abstract
During 1968-1971 Japanese encephalitis (JE) surveillance was conducted in Taiwan. Active case-finding by hospital visits, blood collection from every patient at the suitable time, and the enforcement of standard diagnostic criteria on the results of hemagglutination-inhibition tests were emphasized. Each year, about 90% of reported patients were etiologically examined. JE virus etiology was established in 277 (1968), 279 (1969), 269 (1970) and 158 (1971) cases. Despite the apparent concentration of cases in several cities, practically all the cultivated plains and basins were established as potentially endemic for JE. JE outbreak is clearly associated with season in subtropical and tropical Taiwan. Each year it occurred consistently in mid July in the southernmost county, 2-3 wk after the peak of rice transplantation, and its duration was a few weeks. On the western side of the island, although less consistently, JE outbreak seems to occur 1-3 wk later than in the south. Outbreak in E Taiwan was a mid-Sept. phenomenon for 3 yr. Observed seasonal lag, significant between 2 neighboring localities at the same latitude, suggests that paddy water management is more directly related to date of outbreak than local climate. The area may be separated into 8 ecologic subdivisions. JE-virus transmission to a man during April at temperatures below the average of 20.degree. C is discussed.

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