Transmissibility of Hand, Foot, and Mouth Disease in 97 Counties of Jiangsu Province, China, 2015- 2020

Background: Hand, foot, and mouth disease (HFMD) has been a serious disease burden in the Asia Pacific region represented by China, and the transmission characteristics of HFMD in regions haven’t been clear. This study calculated the transmissibility of HFMD at county levels in Jiangsu Province, China, analyzed the differences of transmissibility and explored the reasons. Methods: We built susceptible-exposed-infectious-asymptomatic-removed (SEIAR) model for seasonal characteristics of HFMD, estimated effective reproduction number ( R eff ) by fitting the incidence of HFMD in 97 counties of Jiangsu Province from 2015 to 2020, compared incidence rate and transmissibility in different counties by non -parametric test, rapid cluster analysis and rank-sum ratio. Results: The average daily incidence rate was between 0 and 4 per 100,000 in Jiangsu province from 2015-2020. The 97 counties could be divided into three levels: low incidence, medium incidence and high incidence, and occurred that the average daily incidence rate dropped sharply in 2016-2017, and increased sharply in 2017-2018 years. The Quartile of Reff in Jiangsu Province from 2015 to 2020 was 1.54 (0.49, 2.50), Rugao district in Central Jiangsu and Jianhu district in Northern Jiangsu had the highest transmissibility by rank-sum ratio. R eff generally decreased in 2017 and increased in 2018 in most counties, and the median level of R eff was lowest in 2017 ( P <0.05). Conclusion: Transmissibility was different in 97 counties of Jiangsu Province, and the reasons for the differences may be related to the climate, demographic characteristics, virus subtypes, vaccination and other infectious diseases.