Background Several countries adopted lockdown to slowdown the exponential transmission of the coronavirus disease (COVID-19) epidemic. Disease transmission models and the epidemic forecasts at the national level steer the policy to implement appropriate intervention strategies and budgeting. However, it is critical to design a data-driven reliable model for nowcasting for smaller populations, in particular metro cities. Objective The aim of this study is to analyze the transition of the epidemic from subexponential to exponential transmission in the Chennai metro zone and to analyze the probability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) secondary infections while availing the public transport systems in the city. Methods A single geographical zone “Chennai-Metro-Merge” was constructed by combining Chennai District with three bordering districts. Subexponential and exponential models were developed to analyze and predict the progression of the COVID-19 epidemic. Probabilistic models were applied to assess the probability of secondary infections while availing public transport after the release of the lockdown. Results The model predicted that transition from subexponential to exponential transmission occurs around the eighth week after the reporting of a cluster of cases. The probability of secondary infections with a single index case in an enclosure of the city bus, the suburban train general coach, and the ladies coach was found to be 0.192, 0.074, and 0.114, respectively. Conclusions Nowcasting at the early stage of the epidemic predicts the probable time point of the exponential transmission and alerts the public health system. After the lockdown release, public transportation will be the major source of SARS-CoV-2 transmission in metro cities, and appropriate strategies based on nowcasting are needed.
【저자키워드】 COVID-19, Epidemic, mathematical modeling, public transport, probabilistic models, exponential transmission, 【초록키워드】 coronavirus disease, public health, SARS-CoV-2, coronavirus, lockdown, Intervention, Transmission, progression, Probability, SARS-CoV-2 transmission, Secondary infection, Cluster, Transmission model, Critical, early stage, predict, COVID-19 epidemic, index case, Chennai, Transport, acute respiratory syndrome, District, zone, National, objective, populations, country, data-driven, the epidemic, Result, predicted, applied, occur, adopted, 【제목키워드】 SARS-CoV-2, prediction, Chennai, transition,