An international team of scientists has found evidence of an epidemic of an unknown coronavirus or a similar pathogen that struck the East Asian region more than 20 thousand years ago. The genetic traces of the outbreak are still present in the genomes of people living in this region. The results of the study are published in the journal Current Biology.
The researchers analyzed data from the 1000 Genomes Project, which is the largest publicly available catalog of common human genetic variations. Their goal was to find out whether the ancient coronavirus epidemics, if there were any, could somehow affect a person’s susceptibility to viruses, including SARS-CoV-2, at present.
It is known that natural selection in the past contributed to the spread in the human population of such genes that encoded proteins that physically interact with viruses (virus-interacting proteins, VIP) and contributed to protection from infections, reducing the severity of diseases. Scientists were looking for characteristic traces of such selection in 420 proteins interacting with coronaviruses (CoV-VIP), among 26 different human populations.
Among all CoV-VIPs, 332 proteins interacted with SARS-CoV-2, and 88 were mentioned in the scientific literature as associated with various coronavirus infections (SARS-CoV-1, MERS, and HCoV-NL63, which causes moderate ARVI). It turned out that the frequency of such genes is significantly increased in many populations of East Asia, which is not observed in other groups of people. This indicates the occurrence of other coronavirus epidemics in the region in the past.
Thus, 42 genes associated with the coronavirus were subjected to coordinated natural selection about 25 thousand years ago, which corresponds to about 900 generations. However, the researchers cannot rule out that the reason for the selection could be another currently unknown type of virus that interacted with human proteins in the same way as coronaviruses.
Among these 42 CoV-VIPs, many variants affect the course of COVID-19 among the modern population. Mutations with proviral or, conversely, protective effects affect those fragments of genes that are located near regulatory regions active in the lungs and other tissues affected by SARS-CoV-2. At the same time, the authors of the article emphasize that the results do not provide evidence of any differences in increased or decreased genetic susceptibility in any human population.
All modern coronavirus outbreaks, including SARS, MERS, and COVID-19, originate from East Asia. As the study shows, this region probably served as a natural reservoir of coronaviruses for the last 25 thousand years.