Epidemiology of leptospirosis in China, 2006-2010

Objective To understand the epidemiological characteristics of leptospirosis in China from 2006 to 2010 and provide evidence for leptospirosis prevention and control. Methods The descriptive analysis was conducted on the incidence data of leptospirosis in China from 2006 to 201 collected from national disease reporting information system and national leptospirosis sentinel surveillance system. Results From 2006 to 2010, the incidence of leptospirosis in China continued to decline, and the average annual case number was 719. The overall case fatality was 2.47%. The cases occurred in 6 provinces in southern China accounted for 74.58% of the national total. The incidence peak was during August-September and the cases during this period accounted for 38.96% of the annual total. Totally 75.24% and 11.01% of the cases were distributed in farmers and students and the cases in people aged＞35 years accounted for 66.82%. The age specific sub-peak of the incidence was in children aged 10-15 years and the peak was in middle aged adults and the elderly. Totally 34 outbreaks of leptospirosis with 174 cases and 39 deaths were reported during this period in China. Among 1020 cases reported by surveillance system, 62.94% had the history of pathogen contaminated water one month before onset, in which 91.74% were infected during work in rice field and recreational activity in water. The disease pathogen was detected in rats, frogs, pigs, cattle and muntiacus, The antibodies to leptospira in serogroup Icterohaemorrhagiae, Grippotyphosa, Australis, Autumnalis and Hebdomadis were most frequently detected in the population. Conclusion The incidence of leptospirosis remained at low level in recent years in China, but the factors which could facilitate the spread of the disease still exist. The case fatality is still high and local outbreaks occur occasionally. The disease situation in southern China is serious with high incidence in summer and autumn. The disease is still mainly caused by the infection when working in rice field. Middle-aged and elder people has become the mostly affected population instead of young adults. The possibility of local leptospirosis outbreak still exists. It is necessary to strengthen the training and health education about leptospirosis prevention and control in medical care providers and general population respectively.