New computer modelling has pinpointed November 17, 2019 as the likely start date of the first human case of SARS-CoV-2 (COVID-19), two weeks earlier than it was first believed the virus was transmitted from an animal to human.
In 2020, COVID-19 then spread from China to Japan on January 3, and reached Europe and North America in mid-January.
Commenting on the findings, Associate Professor Stuart Turville from UNSW Sydney’s Kirby Institute said that modelling such as this was important to understand the virus but always relied on ‘the last known tangible evidence’.
The immunovirology and pathogenesis expert added that what would be very useful for the scientific community to analyse was information about samples taken from Wuhan locals (the area in China where the virus is believed to have originated), dating back earlier than October 2019.
“The World Health Organization (WHO) investigations moving forward may shed more light on the actual dates,” Turville said.
“What will be key is serum sampling and testing in and around that area (Wuhan) and actual definitive results from those types of studies.”
“Unfortunately with […] the sensitivities in doing this follow up research in China, it may be some time till we see reports like that,” he added.
The study was led by the University of Kent’s David Roberts and was published in the PLOS Pathogens on Friday. The modelling used by the Robert’s team to determine the earliest cases of COVID-19 has been previously used by conservation scientists to map animal species at risk of extinction.
Medical epidemiologist Dr Abrar Chughtai from UNSW’s school of public health and community medicine said the results of this new study were interesting, however he also cautioned that modelling studies have limitations because their results rely on specific parameters and data quality.
“We need to conduct more epidemiological, environmental, genetic and modelling studies to confirm these findings,” Dr Chughtai said.
“This may also help in finding the origin of SARS-CoV-2.”
ANU’s Professor Peter Collignon said despite the modelling, he still suspected the COVID-19 virus was around even earlier than November 2019.
The microbiologist and infectious diseases physician referred to suspected positive cases in France and the US in late 2019 to suggest that although high numbers of COVID-19 were not present in those regions until February to March of 2020, ‘it was likely present a couple of months earlier and during their winters, when spread occurs more readily’.
“In France, a man who was ill in late December 2019 was retrospectively identified to have had a severe COVID-19 illness,” Collignon said.
“This implies, given the average incubation period for COVID-19 and additionally the time usually taken to develop severe symptoms leading to hospital admission, that the virus was present in Paris since at least mid-December 2019.”