Abstract: Objective This study was intended tO discuss and explore the epidemiological factors in—volved in the outbreak of viral encephalitis in Jiangsu Province of 2002．Methods Retrospective research was carried Out as for the outbreak of viral encephalitis in 2002 using 1：2 pairing ease control study，in which 1 19 cases of children with onsets of viral encephalitis during the outbreak were classified as case group and 338 students who were of the same grade，similar age and healthy withoUt fever within recent 2 months were sorted into control group．Results 5 epidemic factors that affects the outburst of viral encephalitis were screened Out aided by conditional Logistic regression analysis，namely contact with pa—tients 2 weeks before onsets，presence of patients with viral encephalitis in neighborhood or relatives，no hand washing before meals and after defecation，high density of flies indoors and poor condition in home toilets．Conclusion The outbreak of viral encephalitis in Jiangsu province of 2002 is transmitted by con—tact，fecal—oral and entomophila pathway etc．，and the most effective measure for preventing and con—trolling the disease is tO reduce close contact with patients and care for personal and family sanitation．