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On September 22, researchers from the University of Science and Technology of China and the University of Chinese Academy of Sciences jointly published an article titled "Dating the First Case of COVID-19 Epidemic from a Probabilistic Perspective" on the Chinese Academy of Sciences Scientific Papers Pre-release Platform (ChinaXiv) The research report of the United States used a new big data analysis method to infer the origin time of the COVID-19 pandemic in the United States

The traceability results show that the high probability of "Patient Zero" of COVID-19 in the United States is between August and October 2019.

By observing the positive rate curve of the early novel coronavirus (SARS-COV-2) detection in more than 50 states in the United States, the researchers identified the 13 states and the District of Columbia where the mortality rate peaked in early 2020, and focused on them after consideration.

In this study, the researchers modeled the positive rate of detection in each state to fit the actual development trend of the epidemic, and used least squares estimation to obtain the best model parameters, given a certain confidence probability, Then infer the dates and corresponding probabilities of the first, 50 and 100 SARS-COV-2 infections

The calculation results show that in the 12 regions with the most representative mortality from the early epidemic in the United States, there is a 50% probability that the first infection date will occur between August and October 2019

(Illustration: the date and corresponding probability of the first, 50 and 100 SARS-COV-2 infection cases in 12 regions of the United States)

The researchers also used the daily number of confirmed cases in Wuhan, China and Zhejiang, China to model the number of confirmed cases per day to estimate the occurrence time and corresponding probability of the first, 50, and 100 infected cases

(Illustration: The date and corresponding probability of the first, 50 and 100 SARS-COV-2 infection cases in Wuhan and Zhejiang)

At the end of the report, the researchers pointed out that this method can also help other countries and regions to estimate the origin of the epidemic.