A laboratory scientist cultures coronavirus to prepare for testing at Fort Detrick. Photo: AP

The coronavirus may have been silently spreading in the US in as early as September 2019, a preprint research paper suggested. 

The paper, authored by researchers from the University of Science and Technology of China and the University of Chinese Academy of Sciences, was released on ChinaXiv, a preprint platform developed by the Chinese Academy of Sciences (CAS). 

Combined with mathematical model and artificial intelligence technology, qualitative and quantitative analysis of infectious diseases can reveal the epidemic law of infectious diseases and detect the origin and development trend of infectious diseases, the paper read.

The paper selected 12 representative regions in the US for analysis and found that the date of the first infection was mostly between August and October 2019, which is earlier than the official date of the first confirmed case in the US on January 20, 2020. 

The experimental results indicate that the COVID-19 pandemic in the US started to spread around September 2019 with a high confidence probability.

In addition, the study shows that the existing confirmed cases were also used in Wuhan city and Zhejiang Province in China to infer the time COVID-19 originated and provided results with confidence. The results show that the spread of COVID-19 in China likely began in late December 2019. 

Researchers of the study could not be reached by the Global Times as of press time. An expert, who requested anonymity, from the WHO-China joint expert team on tracing coronavirus origins, told the Global Times that using a mathematic model is a novel way to find coronavirus origins, yet "it wasn't often used and not certain about its accuracy."

Despite this, many Chinese scientists also expressed strong inclination to support WHO to conduct the next stage coronavirus probe in the US, citing evidence that suggested the virus may have emerged in the US earlier than it officially identified.

A study taken for a National Institutes of Health (NIH) research program in the US between January 2 and March 18, 2020 suggested in June that seven people in five states - Illinois, Massachusetts, Mississippi, Pennsylvania and Wisconsin - may have been infected well before the country's first confirmed cases reported on January 21, 2020. 

Zeng Guang, former chief epidemiologist of the Chinese Center for Disease Control and Prevention, said that the evidence suggested that WHO should prioritize the US for the next stage probe of coronavirus origins. 

"The WHO still did not lay out a clear blueprint for the next stage coronavirus origins probe. The US should be a top focus in this process, as there is evidence that the virus had already been circulating in this country months before its first case, and many of its bio-labs are shrouded in secrecy," said Zeng.

He also suggested the WHO trace samples of people who suffered from pneumonia in the past two years in countries where traces of the coronavirus were found earlier than that of the Wuhan outbreak, such as Italy and Spain.

In an exclusive interview with the Global Times in August, Liang Wannian, team leader of the Chinese side of the WHO-China joint expert team, said that for the second-stage investigation, the WHO should carry out research in countries where earlier suspected cases had been reported or where novel coronavirus was detected in samples earlier than the Wuhan outbreak. 

"The next stage of study should refer to the research framework and method of the virus origins probe conducted in China. The WHO should carry out research in countries where sewage, serum, human or animal tissue or swab and other samples tested positive for SARS-CoV-2 before the end of 2019 to further understand the origins of the virus in local places and possible human infection status. Some of the research may have been partially completed or documented. The second-stage research should build on existing information, reinforce the work rather than duplicate ongoing or existing work," Liang said. 

Whether it is early cases, biological samples, gene sequences, natural hosts, intermediate hosts, or cold chains, it is necessary to carry out joint research in many countries, many places around the world, Liang stressed.