Epidemiological survey of the first outbreak of dengue fever in island area, Zhejiang Daishan county

ObjectiveTo explore the epidemiological characteristics of the first outbreak of dengue fever in islands area of Zhejiang province and provide evidences for dengue fever prevention and control in island area.

MethodsCase search was conducted in Jiangnan village and all the medical institutions. Epidemiological investigation and response were conducted for all the cases. Serum samples were collected from the cases for the detection of dengue virus nucleic acid and antibody, and the E gene of the viral nucleic acid was amplified and sequenced, and a phylogenetic tree was constructed to trace the possible source of infection.

ResultsA total of 9 cases was reported in this outbreak, no severe cases and deaths occurred. The outbreak lasted 15 days, the male to female ratio of the cases was 1∶8, the age of the cases ranged from 25 years to 77 years. Analysis on the E gene sequence of the amplified strain revealed that the local outbreak virus belonged to dengue virus type I (DENV-1). It was found to be highly homologous with four strains from Vietnam in 2017 (LC428079, LC428073, LC428062, LC428059: similarity 99.81%), 1 strain from Cambodia to Henan in March 2019 (MK905537: similarity 99.75%); 1 strain from Singapore in 2016 (MF033254: similarity 99.68%), and 1 strain from Cambodia to Lishi of Zhejiang province in June 2019 (MN444624: similarity 99.62%).

ConclusionThis dengue fever outbreak was caused by DENV-1, and result suggested that the patriotic health campaign is needed to carry out to eliminate mosquito-borne breeding sites and reduce the density of mosquito vector, and clinician training for dengue fever identification and diagnosis should be strengthened.