A small fragment of genetic code inherited from Neanderthals may increase the risk of severe illness from COVID-19.
The stretch of DNA, spanning six genes, is more common in South Asian populations than in Europeans, according to the study published on bioRxiv, which is yet to be peer-reviewed. It is not yet known why this particular segment increases the risk of developing a severe form of COVID-19 requiring ventilation after infection with the virus, SARS-CoV-2.
'This interbreeding effect that happened 60,000 years ago is still having an impact today,' Dr Joshua Akey, a geneticist from Princeton University, New Jersey, who was not involved in the study, told the New York Times.
In a separate study published last month, scientists identified a cluster of genes on chromosome three, that were more common among COVID-19 patients with respiratory failure. The authors used an online genome database to link this genetic sequence to the remains of a Neanderthal found in Croatia around 50,000 years ago.
According to the researchers, the ‘Neanderthal' genetic signature is more common in people from South Asia, where 30 percent of the population have at least one copy, compared to around eight percent in Europe and four percent in East Asia. The genetic variant is most common in Bangladesh, where 63 percent have inherited the segment, while it is almost completely absent in African populations.
Study author, Dr Hugo Zeberg from the Karolinska Institutet in Sweden and the Max Planck Institute for Evolutionary Anthropology, Germany, told the New York Times that the reason for the evolutionary pattern of distribution is uncertain. It is possible that the gene variant may have once been favourable for providing a strong immune response to viruses.
'One should stress that at this point this is pure speculation,' cautioned co-author Professor Svante Pääbo from the Max Planck Institute and Okinawa Institute of Science and Technology in Japan.
The link between the Neanderthal segment and COVID-19 risk may become clearer as researchers study more patients. 'Its evolutionary history may give us some clues,' Dr Zeberg concluded.