Risk assessment on importation and autochthonous transmission of Zika virus disease in the mainland of China, 2016

Abstract

Word Health Organizaiton has declared the clusters of microcephaly cases and other neurological disorders constituted a Public Health Emergency of International Concern on 1 Feberuary 2016, and there is increasing evidence that they are causal related with Zika virus. Zika virus disease has been identified in 41 countires and areas since 2015, and it is spreading to the other parts of the world. There were 10 imported cases of Zika virus disease detected in the mainland of China from January to February 2016, without autochthonous transmission. In order to identify the risk of importation and autochthonous transmission of Zika virus disease in the mainland of China from March to December, 2016, we conducted a qualitative and quantitative risk assessment. We assumed that the Zika virus might have the similar transmission pattern as dengue virus. The surveillance data of dengue fever in the mainland of China were analyzed for infering the importation and local transmission of Zika virus. Travelling between China and those areas with Zika virus autochthonous transmission was used to assess the risk of importation. Surveillance and border investigation information of Aedes aegypti and Aedes albopictus, and the urbanization rates of each provinces in 2015 were used to assess the risk of autochthonous transmission. There would be more imported cases of Zika virus disease detected in the mainland of China, the total case number might be 8-68 from March to December 2016 if there was no big outbreak of Zika virus disease in Southeast Asia, and the total case number might be up to 106-876 if the epidemic situation of Zika virus disease was similar as dengue in Southeast Asia. The period at the highest risk for autochthonous transmission of Zika virus in the mainland of China would be between June and October; the regions at the highest risk of autochthonous transmission minght be Guangdong, Yunnan, Hainan, Fujian, Guangxi and Zhejiang; there was with some risk of autochthonous transmission for the other provinces with Aedes albopictus; and there is no risk of autochthonous transmission for the regions of Inner Mongolia, Jilin, Heilongjiang, Qinghai, Xinjiang, and those areas without Aedes albopictus in Liaoning, Shaanxi, Gansu and Tibet. We suggest that all provinces should continue to monitor the possible imported cases of Zika virus disease; provinces at risk of of autochthonous transmission should strengthen the mosquito surveillance during the mosquito active seasons and control the vector density; travellers to areas with Zika virus outbreaks should be provided with up to date health information and pregnant women should avoid travelling to those areas; and dynamic risk assessment should be carried out according to the epidemic situation and research progress.