Where did Coronavirus pandemic originate? Scientists now believe it may NOT have started in Wuhan!
The coronavirus pandemic may have started between mid-September and early December, and it may not have originated in Wuhan, says a researcher.
A group of scientists from Cambridge, UK, and Germany have reconstructed the early “evolutionary paths” of COVID-19 in humans—as the infection spread from Wuhan out to Europe and North America—using genetic network techniques. They subsequently extended the analysis to 1,001 viral genomes. While yet to be peer-reviewed, geneticist Dr Peter Forster, who is leading the study from the University of Cambridge, says the latest work suggests that the first infection and spread among humans of COVID-19 may have occurred between September 13 and December 7.
“This assumes a constant mutation rate, which is admittedly unlikely to be the case, and the time estimate could, therefore, be wrong. But it is the best assumption we can make at the moment, pending analysis of further patient samples stored in hospitals during 2019,” Dr Forster told Newsweek.
“The virus may have mutated into its final ‘human-efficient’ form months ago, but stayed inside a bat or other animal or even human for several months without infecting other individuals. Then, it started infecting and spreading among humans between September 13 and December 7, generating the network we present in Proceedings of the National Academy of Sciences (PNAS),” he told the South China Morning Post (SCMP)
In the previous study, published in PNAS, the research team had discovered three distinct strains of COVID-19, consisting of clusters of “closely related lineages” — which have been labeled ‘A’, ‘B’ and ‘C’.
They used data from virus genomes sampled from across the world between December 24, 2019, and March 4, 2020, and created the evolutionary path of COVID-19. By analyzing the first 160 complete virus genomes to be sequenced from human patients, the scientists mapped some of the original spread of the new coronavirus through its mutations, which creates different viral lineages.
The researchers found that the closest type of COVID-19 to the one discovered in bats — type A, the “original human virus genome” — was present in Wuhan, but surprisingly was not the city’s predominant virus type. Mutated versions of ‘A’ were seen in Americans reported to have lived in Wuhan, and a large number of A-type viruses were found in patients from the US and Australia.
Wuhan’s major virus type, ‘B’, was prevalent in patients from across East Asia. However, the variant did not travel much beyond the region without further mutations, indicating “a founder event in Wuhan, or resistance against this type of COVID-19 outside East Asia,” says the study.
According to the researchers, the ‘C’ variant is the major European type, found in early patients from France, Italy, Sweden, and England. It is absent from the study's Chinese mainland sample but seen in Singapore, Hong Kong, and South Korea.
The analysis also suggests that one of the earliest introductions of the virus into Italy came via the first documented German infection on January 27 and that another early Italian infection route was related to a “Singapore cluster.” “The viral network we have detailed is a snapshot of the early stages of an epidemic, before the evolutionary paths of COVID-19 become obscured by vast numbers of mutations,” says Dr Forster in the analysis.
The researchers aim to find out “patient zero” (the index patient who was the source of a local outbreak) to help identify relevant virus types for the design of clinical tests, medication and vaccines. Since the previous paper had a small sample size, it limited the researchers’ ability to determine when and where the first outbreak started. Accordingly, the analysis was extended to over 1,000 viral genomes. “It is possible the outbreak did not originate in Wuhan, as until January 17, almost all the isolates were type B. In Guangdong, a province about 500 miles from Wuhan, seven of the 11 isolates were type A. These case numbers are small because few genomes are available for the early stage of the outbreak before the Chinese New Year travel pre-January 25 would have started mixing patterns up geographically,” Dr Forster told Newsweek.
He told SCMP that if pressed for an answer, he would say the original spread started more likely in southern China than in Wuhan. “But proof can only come from analyzing more bats, possibly other potential host animals, and preserved tissue samples in Chinese hospitals stored between September and December. This kind of research project would help us understand how the transmission happened, and help us prevent similar instances in the future,” said Dr Forster.