Abstract: 【Abstract】 Objective To make a field investigation on the affecting factors of malaria outbreak in a village of Congjiang County, Guizhou Province. Methods The investigation was made in August， 2006. Filter paper dry blood samples were taken for indirect fluorescent antibody test (IFAT) from all the 495 residents above 1 year-old in the village where an outbreak of malaria was reported. Questionnairing was conducted in 423 villagers over 10 years-old, covering malaria history in the past 2 years, knowledge on malaria and its control, use of mosquito nets, and out-door sleeping habit. Data on febrile outpatients were collected from the records of the township health center for analyzing the compliance of the patients in seeking medical services. Mosquito collecting by human-bait before mid-night, and in mosquito nets and cattle pens in early morning was performed for mosquito composition and man-biting rate. Results Re-examination of the 42 positive blood smears confirmed 12 positives of P.vivax infection. The malaria incidence in 18 d was 2.1%，including 4 cases clinically diagnosed. The antibody positive rate of IFAT in the population was 8.7% (43/495) with a positive GMRT of 20.6, overall GMRT of 10.6; the IFAT positive rate in the age group of under 5 was 7.5% (3/40) with a GMRT of 25.1. The rate of seeking medical advice among febrile patients was 81.3% (118/145), 78.8% (93/118) of which being in the village clinic. The average time of going to a doctor after fever was 3.9 days, 37.4% (195/521) and 3.3% (17/521) were in 4-6 days and over 10 days respectively， with the longest 26 days. The average knowledge rate on malaria was 25.5% (108/423), with 17.1%, 29.2% and 40.0% in the groups of illiteracy, primary school and high school education respectively. A statistical significance was found between primary school/high school education and the illiteracy （P＜0.01）. The average rate of using mosquito nets was 31.0% (131/423), out-door sleeping rate was40.7% (172/423). The radical cure rate in 2004 and 2005 was 68.2% (15/22) and 48.3% (14/29) respectively. In addition to Anopheles sinensis, An. anthropophagus and An. minimus also existed in rooms and nets with a man-biting rate of 0.0566 and 0.0755 respectively. Conclusions Three species of anopheline mosquitoes are the important transmitting vectors. Poor self-protection, outdoor sleeping habit, delayed examination and treatment, and irregular chemotherapy among the residents are the main factors resulting malaria outbreak.

Key words: Malaria, Outbreak, Affecting factor