Using the same techniques used to map the movements of prehistoric human populations through the analysis of DNA mutations, a team of scientists from various institutions in the United Kingdom and Germany has reconstructed the first movements of the SARS-CoV infection. 2 from its epicenter in the Chinese city of Wuhan to the rest of the world. The result, a kind of snapshot of the origins of the pandemic, has been published in the journal Proceedings of the National Academy of Sciences (PNAS).
The scientists used the first 160 complete genomes of the virus that were sequenced from human patients to reproduce part of the initial spread of the new coronavirus through its mutations. Specifically, the genome data was collected from people around the world between December 24, 2019 and March 4, 2020. The results revealed three different variants of the virus, which would actually be groups made up of closely related lineages. and which they named ‘A’, ‘B’ and ‘C’.
One of the first surprises found was that the type of coronavirus most similar to that discovered in bats and pangolins (type ‘A’), was present in Wuhan, but it was not the most abundant. This variant has been identified in Chinese patients and in Americans residing in Wuhan. Additionally, mutated versions of ‘A’ were found in other patients from the US and Australia.
The ‘B’ variant would have been the most prevalent in East Asia , but it did not go much further, which according to the researchers could be due to two reasons: one would be a phenomenon that in evolution is known as the ‘founder effect’. This is a genetic bottleneck that occurs when a new type of virus establishes itself from a small isolated group of infections.
Another explanation that, according to the authors, would be worth considering, refers to the development of some type of resistance against this variant of the infection outside of East Asia. “It seems that, in this early phase, we see a slower mutation rate in East Asia than elsewhere,” explains Peter Forster, a researcher at the University of Cambridge and lead author of the work. “The type ‘B’ virus could adapt immunologically or environmentally to a large part of the East Asian population, but it may have to mutate to overcome that resistance outside of that region,” he argues.
The European variant
The coronavirus called ‘type C’ would have been the most abundant in Europe, at least at the beginning of the infection, and this variant was isolated in the first cases detected in France, Italy, Sweden and England. It has also been found in patients from Singapore, China, Hong Kong and South Korea, but not in the sample from mainland China.
The researchers highlight that these phylogenetic analysis techniques can be useful in tracing possible routes of infection and applied to the latest coronavirus genome sequencing to help predict future hot spots where the infection could flare up again to adequately contain it.
It should also be taken into account that this analysis was done with data obtained just at the beginning of the outbreak of COVID-19. “The viral network that we have detailed in the article is just a snapshot of the early stages of the epidemic, before all the evolutionary changes suffered by the virus were obscured by the large number of mutations,” explains Forster. ” It’s like catching a supernova right at the beginning of the explosion, ” he concludes.
