| Zika virus（ZIKV）has caused a serious public health crisis worldwide.Its transmission routes include vector（Aedes albopictus and Aedes aegypti）transmission,sexual transmission and vertical transmission.Patients are mostly recessive.The infectious period is not yet clear.The Zika epidemic continues to spread around the world,mainly in countries and regions such as the America,Africa,Southeast Asia,and Pacific island countries.The epidemic has attracted high attention from the public health department.It is necessary to study the transmission mechanism and risk analysis of Zika virus.To explore the transmission mode of ZIKV,a dynamic process-based epidemiological ordinary differential equation model is firstly proposed,which embeds human-mosquito transmission through bites and sewage,as well as human-to-human transmission through sexual behavior and mosquito infection through bites.Mathematical analysis is performed to calculate the basic reproduction number,calculate the backward branch,and prove the existence and stability of the equilibrium point.Fitting the Brazilian epidemic data from January 2015 to September 2016 by the Markov Chain Monte Carlo method,these are found that（1）the estimated reproduction number 0R is estimated to be 2.13,in which the contributions by mosquito bite,sex and sewage account for 85.7%,3.5%and 10.8%,respectively;（2）0R and morbidity are most sensitive to parameters related to mosquito ecology,rather than asymptomatic or human-human transmission;and（3）multiple transmission routes and suitable temperature exacerbate ZIKV infection in Brazil.Secondly,the aim of this paper is to estimate the risk of Zika and dengue infection that imports from Asia and causes local outbreaks.Based on the oversea epidemic data and the floating population between 2015 and 2017,an input model was built to estimate the number of imported cases,and the local epidemic transmission probability and basic regeneration number were calculated via the branching process under different temperatures and herd immunity levels.It is found that（1）the optimum temperature for Zika and dengue transmission is around 28.9℃,in which the risk probability of local transmission is 24.4%and 99.9%,respectively;（2）when the human herd immunity level is0,0.2 and 0.6,the basic reproduction numbers of Zika and dengue are 8.1,6.7,3.2 and 3.2,2.7,1.3,respectively;（3）the imported cases mainly come from South Asia.South-central and south-eastern China are top-risk areas for local transmission,especially in June-August;（4）the infection in Singapore is more likely to cause Zika outbreak in China,while the infection in Thailand,Vietnam,Malaysia and Singapore are the biggest cause of local transmission of dengue fever in China. |
