Title: Arbovirus infections in the mosquitoes of Fukuoka area, Kyushu, Japan : 4. The epidemiological relations among the seasonal prevalence of the vector mosquitoes of Japanese encephalitis virus, the natural infection of the mosquitoes and the epidemic sizes of Japanese encephalitis
Abstract: Light-trap studies on the seasonal prevalence of Culex tritaeniorhynchus Giles were conducted during the period from 1963 to 1972 in specified study sites of the Fukuoka area. The results of the studies are subject to the inquiries into the relations with the natural infection patterns of the mosquito with Japanese encephalitis virus and the epidemic sizes of Japanese encephalitis. The vector populations had been infected in their increasing phases in the severe epidemic period before 1967 but often in their decreasing phases in the mild epidemic period after 1966. The period changes in mode of vector infection and epidemic size might be attributed to a chronic tendency towards decline of vector populations. Despite of the above facts, the annual variation in the onset time of vector infection was responsible for year-to-year fluctuation in epidemic size in the mild epidemic period as well as in the severe epidemic period.