Coronavirus circulated undetected months before first COVID-19 cases in China: Study

The novel coronavirus was likely circulating undetected for at most two months before the first human cases of COVID19 were described in Wuhan China in lateDecember 2019 according to a studyThe research published in the journal Science used molecular dating tools and epidemiological simulations to date the emergence of the virus to as early as October 2019The team including researchers from University of California San Diego in the US note that their simulations suggest that the mutating virus dies out naturally more than threequarters of the time without causing an epidemicOur study was designed to answer the question of how long could SARSCoV2 have circulated in China before it was discovered said senior study author Joel O Wertheim an associate professor at UC San Diego School of MedicineTo answer this question we combined three important pieces of information a detailed understanding of how SARSCoV2 spread in Wuhan before the lockdown the genetic diversity of the virus in China and reports of the earliest cases of COVID19 in China Wertheim saidBy combining these disparate lines of evidence the researchers were able to put an upper limit of midOctober 2019 for when SARSCoV2 started circulating in Hubei provinceCases of COVID19 were first reported in lateDecember 2019 in Wuhan located in the Hubei province of central ChinaThe researchers used molecular clock evolutionary analyses to try to home in on when the first or index case of SARSCoV2 occurredMolecular clock is a term for a technique that uses the mutation rate of genes to deduce when two or more life forms diverged in this case when the common ancestor of all variants of SARSCoV2 existed estimated in this study to as early as midNovember 2019Molecular dating of the most recent common ancestor is often taken to be synonymous with the index case of an emerging diseaseThe index case can conceivably predate the common ancestor the actual first case of this outbreak may have occurred days weeks or even many months before the estimated common ancestor said study coauthor Michael Worobey a professor at the University of ArizonaDetermining the length of that phylogenetic fuse was at the heart of our investigation Worobey saidBased on this work the researchers estimate that the median number of persons infected with SARSCoV2 in China was less than one until November 4 2019Thirteen days later it was four individuals and just nine on December 1 2019 they saidThe first hospitalisations in Wuhan with a condition later identified as COVID19 occurred in midDecemberThe researchers used a variety of analytical tools to model how the SARSCoV2 virus may have behaved during the initial outbreak and early days of the pandemic when it was largely an unknown entityThese tools included epidemic simulations based on the viruss known biology such as its transmissibility and other factorsIn just 297 per cent of these simulations was the virus able to create selfsustaining epidemicsIn the other 703 per cent the virus infected relatively few persons before dying out The average failed epidemic ended just eight days after the index caseWe saw that over twothirds of the epidemics we attempted to simulate went extinct That means that if we could go back in time and repeat 2019 one hundred times two out of three times COVID19 would have fizzled out on its own without igniting a pandemicrdquo Wertheim notedThis finding supports the notion that humans are constantly being bombarded with zoonotic pathogens he addedThis story has been sourced from a third party syndicated feed agencies Midday accepts no responsibility or liability for its dependability trustworthiness reliability and data of the text Midday managementmiddaycom reserves the sole right to alter delete or remove without notice the content in its absolute discretion for any reason whatsoever