When and Where Was the COVID-19 Pandemic Onset?
A new analysis using methods from conservation science suggests that the first case of COVID-19 arose between early October and mid-November 2019 in China.
Evidence is building that its origin as a zoonotic spillover occurred before the officially accepted timing of December 2019, reported this study published by PLOS on June 24, 2021.
In the same way, extinction events are rarely observed, so too are origination events such as those of COVID-19.
David Roberts of the Durrell Institute of Conservation and Ecology, School of Anthropology & Conservation, Marlowe Building, University of Kent, Canterbury, Kent, UK, and colleagues present these findings to help clarify the onset of the COVID-19 pandemic.
Roberts and colleagues repurposed a mathematical model (Optimal Linear Estimation) initially developed by conservation scientists to determine the extinction date of a species based on recorded sightings of the species.
For this analysis, they reversed the method to determine the date when COVID-19 most likely originated, according to when some of the earliest known cases occurred in 203 countries.
The analysis suggests that the first case occurred in China between early October and mid-November of 2019. The first case most likely arose on November 17, 2019, and the disease spread globally by January 2020.
These findings support growing evidence that the pandemic arose sooner and grew more rapidly than initially accepted.
The analysis also identified when COVID-19 is likely to have spread to the first five countries outside of China and other continents.
For instance, it estimates that the first case outside of China occurred in Japan on January 3, 2020, the first case in Europe occurred in Spain on January 12, 2020, and the first case in North America occurred in the United States on January 16, 2020.
These may represent isolated cases, infections that did not contribute to the eventual spread of COVID-19 through the country or territory. However, currently, only the results of retrospective testing have been published for Italy as described above.
Without such analyses, it is impossible to determine if our results have identified early isolated cases or simply reflect inadequate surveillance and pre-symptomatic transmission, stated by these researchers.
Roberts stated in a press release issued on June 24, 2021, "The method we used was originally developed by a colleague and me to date extinctions. However, here we use it to date the origination and spread of COVID-19.”
“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 researchers note that their novel method could be applied to understand better the spread of other infectious diseases in the future.
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