• Kenji Mizumoto, Katsushi Kagaya, and Gerardo Chowell.
• Graduate School of Advanced Integrated Studies in Human Survivability, Kyoto University, Yoshida-Nakaadachi-cho, Sakyo-ku, Kyoto, Japan; Hakubi Center for Advanced Research, Kyoto University, Yoshidahonmachi, Sakyo-ku, Kyoto, Japan; Department of Population Health Sciences, School of Public Health, Georgia State University, Atlanta, GA, USA. Electronic address: mizumoto.kenji.5a@kyoto-u.ac.jp.
• Int. J. Infect. Dis. 2020 Aug 1; 97: 96-101.

ObjectivesThe novel coronavirus (SARS-CoV-2) originating from Wuhan spread rapidly throughout China. While its origin remains uncertain, accumulating evidence links a wet market with the early spread of SARS-CoV-2 in Wuhan. Similarly, the influence of the marketplace on the early transmission dynamics is yet to be investigated.MethodsUsing 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 market-to-human and human-to-human transmission, the reporting probability, and the early effects of public health interventions.ResultsWe 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.ConclusionsOur R estimate tied to market-to-human transmission had substantial uncertainty, but it was significantly lower compared with 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.Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.

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