| IntroductionDengue is a mosquito-borne viral infectious disease, with the main transmission vectors being Aedes aegypti and Aedes albopictus. In China, the main transmission vector is Aedes albopictus for its wide distribution. DENV comprises of four antigenically distinct serotypes (DENV 1-4). Lifelong immunity can be induced when being infected with one specific serotype, but can cause severe dengue when infected with other serotypes. Dengue is endemic in more than 100 countries in tropical and subtropical areas especially in Southeast Asia, the Americas, the western Pacific, Africa and Eastern Mediterranean area, and dengue is expanding to dengue free areas. The incidence has increased 30 fold in the past 50 years. Dengue causes a high economic burden in the world and has become a serious public health problem. Therefore, WHO has defined a global strategy for dengue prevention and control, 2012-2020, aimed to reduce mortality and morbidity from dengue at least 50% and 25% by 2020 respectively.There were no cases reported from establishment of China to 1977. Foshan city, Guangdong Province occurred the first dengue outbreak in 1978.In 1980s, dengue was epidemic in Hainan Province, Guangdong Province and Guangxi Province, and dengue mainly occurred in Guangdong Province in 1990s. During the forty years, large epidemics occurred in Guangdong Province many times, and the outbreak in 2014 was unprecedented, besides which, outbreaks in small scale occurred frequently, which has been a serious public health problem in China. Understanding the dengue situation and the risk factors which were associated with dengue occurrence in China was very important to dengue prevention and control. Therefore, the study would identify that dengue was endemic or not and the risk factors being associated with dengue occurrence, and build the dengue decision support system framework to provide sound evidence for dengue prevention and control.Methods and principal findingsCombining epidemiological characteristics of dengue from the disease notification system, phylogenetic and phylogeographic analyses, results showed that all four serotypes had been detected in Guangzhou, China, which was dominated by DENV 1-2. The Maximum Likelihood tree analytic results showed that the virus detected in Guangzhou localized in different clades, except for virus of 2002 and 2003 clustered together. There existed the mutual introductions between Guangzhou and Southeast Asia. Most of the viruses were imported from Southeast Asia and the sources of outbreaks in Guangzhou mainly originated from Thailand, Indonesia, and the Philippines.The study conducted in Liwan, Yuexiu, Haizhu and Baiyun district showed that local dengue occurrence had a seasonal pattern and the epidemic months were from August to November. Using general linear model based on Poisson distribution, data from 2006 to 2011 showed that local DF cases were positively associated with mosquito density, imported cases, temperature, precipitation, vapour pressure and minimum relative humidity with different time lags, whilst being negatively associated with air pressure, with different time lags.Using generalized additive model based on Poisson distribution, data from 2006 to 2014 showed that local dengue cases in the previous month, minimum temperature in the previous month was positively associated with local dengue occurrence linearly, and imported cases in the previous month, accumulative precipitation with three month lags were positively associated with local dengue occurrence non-linearly. Imported cases in the previous month, minimum temperature in the previous month and accumulative precipitation with three month lags could project the dengue outbreaks occurred in 2013 and 2014 after controlling the autocorrelation, seasonality and long-term trend.Through integrating datasets including mosquito density data, mosquito insecticide resistance data, mosquito infected data, dengue case data, meteorological data, and international dengue data, and using Geographic Information System, SaTScan and R software to analyze including mosquito density interpolation, dengue prediction, dengue outbreak early detection and so on, the output mediated by Google Earth, or in the format of map, graph, table and so on would be aided in dengue risk assessment, intervention and decision support.ConclusionsThe study indicates that dengue in China still remains as an imported disease, with the possibility of localization. Together with the sole transmission vector Aedes albopictus, imported cases, monthly minimum temperature and monthly accumulative precipitation may be used to develop a low-cost effective early warning system. The dengue decision support system would be dynamic and visualized in aiding real-time dengue prevention and control.
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