Objectives To study the time-series of meteorological factors and the reported incidence of Japanese Encephalitis in the southeast of Gansu Province.

Methods The meteorological data of average temperature, relative humidity and rain precipitation of a month and the reported incidence of Japanese Encephalitis from the Infectious Disease Reporting System of Gansu Province in January 2004 to December 2008 were collected.The time-series analysis was explored by using poisson generalized additive model (GAM) with cubic smooth splines.The minimum AIC was used as the criteria of choosing variables and the degree of freedom of their cubic smooth splines.

Results The impact of meteorological factors on the lag time of the onset of Japanese Encephalitis were:3 months for average temperature and precipitation of the month, and 1 month for relative humidity of the month.Increasing 1℃ of average temperature, 1%of average relative humidity and 1mm of precipitation, the relative risk for Japanese Encephalitis increased 2.12, 1.15 and 1.03, respectively.

Conclusions There was a hysteresis effect of meteorological factors on the incidence of Japanese Encephalitis, the increase of temperature, relative humidity and rain precipitation could promote the incidence of Japanese Encephalitis.