[An epidemiological study of the residual vivax malaria cases in Huanghuai plain].

In order to get more knowledge of the epidemiological characteristics of the residual cases of vivax malaria in Huanghuai Plain at the present time, a case-control study was carried out from March to May, 1986 in Zhoukou Prefecture, Henan Province and in Xuzhou City, Jiangsu Province. In both areas, the incidence of vivax malaria in 1985 was lower than 1%. The data were analyzed with the conditional logistic multi-regression model and calculated by using Apple II microcomputer. All the malaria cases selected were within an interval less than 20 days (N.B. The incubation interval of vivax malaria is 20 days) during the transmission season because the cases should be independent of each other and fit with logistic multi-regression model. Three controls were matched for each case at random, including a neighbour person in the same village and a person outside the village. The questionnaire contained a total of 31 relevant items of the subjects, families and villages. Six risk factors (personal history of malaria, family member's history of malaria, number of cases in the village in 1984, direction of breeding place, using mosquito-net and number of livestock) related to malaria transmission were obtained through the analysis of the model. The results were in accord with actual epidemiological characteristics in the region, indicating that the conditional logistic multi-regression model can be applied to epidemiological analysis (study) under controlled conditions and provided quantitative method for analysis of socio-economic effects on malaria. The distribution of the cases and their affecting factors were discussed.