Spatial-temporal Analysis of Malaria and the Effect of Environmental Factors on its Incidence in Yongcheng, China, 2006-2010

BMC Public HealthBMC Public Health 2012, 12:544

Yan Zhang, Qiyong Liu, Rongsheng Luan, Xiaobo Liu, Guangchao Zhou, Jingyi Jiang, Hongsheng Li and Zhifang Li

“Background: In 2003, Plasmodium vivax malaria has re-emerged in central eastern China including Yongcheng prefecture, Henan Province, where no cases have been reported for eleven years. Our goal was to detect the space-time distribution pattern of malaria and determine significant environmental variables contributing to malaria incidence in Yongcheng from 2006 to 2010, thus providing scientific basis for further optimizing current malaria surveillance and control programs.

“Methods: This study examined spatial and temporal heterogeneities in the risk of malaria and the influencing factors on malaria incidence using geographical information system (GIS) and time series analysis. Univariate analysis was conducted to estimate the crude correlations between malaria incidence and environmental variables, such as mosquito abundance and climatic factors. Multivariate analysis was implemented to construct predictive model to explore principal environmental determinants on malaria epidemic using a Generalized Estimating Equation (GEE) approach.

Yearly average temperature at county level from 2006 to 2010 in Yongcheng prefecture, China.

Yearly average temperature at county level from 2006 to 2010 in Yongcheng
prefecture, China.

“Results: Annual malaria incidences at town-level decreased from the north to south, and monthly incidences at prefecture-level demonstrated a strong seasonal pattern with a peak from July to November. Yearly malaria incidence has a visual spatial association with yearly average temperature. Moreover, the best-fit temporal model (model 2) (QIC= 16.934, P<0.001, R2=0.818) indicated that significant factors contributing to malaria incidence were maximum temperature at one month lag, average humidity at one month lag, and the incidence of the previous month.

“Conclusions: Findings support the effects of environment factors on malaria incidence and indicates that malaria control targets should vary with intensity of malaria incidence, with more public resource allocated to controlling source of infections instead of large scale An. sinensis control when malaria incidence is at a low level, which would benefit for optimizing the malaria surveillance project in China and some other countries with unstable or low malaria transmission.”