Effect of the Wet Market on the coronavirus disease (COVID-19) transmission dynamics in China, 2019-2020

Mizumoto, Kenji; Kagaya, Katsushi; Chowell, Gerardo

Abstract Objectives The novel coronavirus (SARS-CoV-2) originating from Wuhan rapidly spread throughout China. While its origin remains uncertain, accumulating evidence links a wet market for the early SARS-CoV-2 spread in Wuhan. Similarly, the influence of the marketplace on the early transmission dynamics is yet to be investigated. Methods Using the daily series of COVID-19 incidence stratified according to contact history with the market, we have conducted quantitative modeling analyses to estimate the reproduction numbers (R) for the market-to-human and human-to-human transmission, the reporting probability and the early effects of public health interventions. Results We estimated R at 0.24 (95%CrI: 0.01-1.38) for market-to-human transmission, and 2.37 (95%CrI: 2.08-2.71) for human-to-human transmission during the early spread in China (2019-2020). Moreover, we estimated that the reporting rate for cases stemming from market-to-human transmission was 2-34 fold higher than that for cases stemming from human-to-human transmission, suggesting that contact history with the wet market played a key role in identifying COVID-19 cases. Conclusions Our R estimate tied to market-to-human transmission has substantial uncertainty, but it was significantly lower compared to the reproduction number driving human-to-human transmission. Our results also suggest that asymptomatic and subclinical infections constitute a substantial component of the COVID-19 morbidity burden.