“The calculations show that the COVID-19 epidemic in the United States has a high probability of starting to spread around September 2019,” said the 14-page paper published Wednesday in ChinaXiv, a repository operated by the National Science Library of the Chinese Academy of Sciences.
The paper was written by Zhouwang Yang, Yunhe Hu, and Zhiwei Ding of the University of Science and Technology of China, and correspondent author Tiande Guo of the Chinese Academy of Sciences.
The quartet set out to infer the time of origin of the pandemic based on data-driven methods and hybrid models.
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“They modeled the rate of positive tests to match actual trends and used least squares estimates to derive optimal model parameters, before applying kernel density estimates to infer pandemic origin times with specific confidence probabilities,” the paper said. Russia Today, Thursday (23/9/2021).
The four researchers also claim that a series of previous studies showed that the United States, Spain, France, Italy, Brazil and other countries had been hit by the coronavirus before its outbreak in China.
Officially, the first case of COVID-19 was registered in the US on January 20, 2020 or about a month after the outbreak in the Chinese city of Wuhan. However, Chinese researchers suggest that there is a 50% chance of the first cases in 11 US states and the District of Columbia before or in early April 2019 in Rhode Island and as late as November of that year in Delaware.
Their sample consisted mostly of the northeastern US states – Massachusetts, Vermont, New Hampshire, Connecticut, Rhode Island, New York, New Jersey, Delaware, Pennsylvania, Maryland and Virginia – with Michigan and Louisiana thrown in as the mix.