Researchers from Nagoya University (Japan) have found that human behavior, including confinements and isolation measures, affects the evolution of new strains of SARS-CoV-2, the virus that causes Covid-19. The coronavirus evolved to become more transmissible earlier in its life cycle.

The study published in Nature Communications provides new insights into the relationship between people’s behavior and disease-causing agents. The researchers used mathematical models with an artificial intelligence component to investigate previously published clinical data and identified trends that suggest human behavior changes designed to limit transmission were increasing selection pressure on the virus.

One important concept in this interaction is the viral charge, which refers to the amount or concentration of a virus present per ml of a body fluid. In the case of SARS-CoV-2, a higher viral load in respiratory secretions increases the risk of transmission through droplets. Viral load relates to the potential to transmit a virus to other people, with viruses like Ebola having an exceptionally high viral load while the common cold has a low one.

The research group led by Professor Shingo Iwami discovered that SARS-CoV-2 variants that were most successful in spreading had an earlier and higher peak in viral load, as well as a shorter duration of infection. They also found that decreased incubation period and increased proportion of asymptomatic infections recorded as the virus mutated affected the evolution of the virus.

Iwami and his colleagues suggest that human behavior changes designed to limit transmission were increasing selection pressure on the virus, causing it to be transmitted primarily during asymptomatic and pre-symptomatic periods, which occur earlier in its infectious cycle. As a result, peak viral load advanced to this period to spread more effectively in these earliest pre-symptomatic stages.

Scientists suggest that when evaluating public health strategies in response to Covid-19 and potentially pandemic-causing pathogens in future

By Editor

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