The World Health Organization was informed about a cluster of unusual pneumonia cases in Wuhan, China, on 31 December 2019.
According to new research, however, the coronavirus may have arisen more than two months earlier.
The infectious outbreak has long been linked to a live animal market in Wuhan at the end of 2019.
Many initially believed the infection "jumped" from an animal into a market worker. Some now wonder whether a coronavirus-positive customer visited the market, turning it into a "superspreading" event.
To better understand the pandemic's onset, scientists from the University of Kent repurposed a mathematical model, originally developed to determine when a species became extinct.
The Kent team reversed the model to uncover when the coronavirus emerged, based on the earliest known cases in more than 200 countries.
Results – published in the journal PLOS Pathogens – suggest the first coronavirus case likely occurred in China on 17 November 2019, but could have fallen anywhere between early October and mid-November.
This follows similar research by the University of California San Diego, which also found "mid-October and mid-November 2019" was the "plausible interval when the first case" of the coronavirus emerged in Hubei province, of which Wuhan is the capital.
When the coronavirus spread beyond China was also somewhat muddled.
In France, the first case was officially recorded on 25 January. Looking back on patient medical records, however, people were in intensive care with a flu-like illness and coronavirus-related lung scans as early as 2 December.
In the US, the first recognised case was reported on 26 February. The coronavirus' genetic material has since been found in an American woman who became ill on 31 January and died on 6 February.
A Chinese researcher has even been accused of deleting data about early coronavirus cases in Wuhan.
The Kent scientists repurposed an extinction model that usually works off the last reported sightings of a specific species.
"Here we use it to date the origination and spread of COVID-19 [the disease caused by the coronavirus]", said study author Dr David Roberts.
"This novel application within the field of epidemiology offers a new opportunity to understand the emergence and spread of diseases as it only requires a small amount of data."
The results suggest the coronavirus "emerged in China in early October to mid-November", with a "likely timing of the first case of COVID-19 as 17 November".
Based on the scientists' model, the coronavirus is likely to have left China on 3 January, entering Japan.
Spain is thought to have had the first European case on 12 January. The coronavirus is then expected to have entered the US four days later, on 16 January.
The scientists hope their novel computer model will help experts better understand the spread of other infectious diseases.
Knowing more about the coronavirus' origin could also enable experts to gauge how the outbreak may continue to evolve.
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