New study published in Nature Communications reveals that human behavior, including confinement and isolation measures, can impact the evolution of new strains of SARS-CoV-2, the virus that causes Covid-19. Researchers led by Professor Shingo Iwami at Nagoya University (Japan) found that the coronavirus evolved to become more transmissible earlier in its life cycle as a result of these behaviors. The study provides new insights into the relationship between people’s behavior and disease-causing agents.
One important factor in this interaction is viral load, which refers to the amount or concentration of a virus present per ml of a body fluid. In the case of SARS-CoV-2, higher viral loads in respiratory secretions increase the risk of transmission through droplets. Viral load relates to the potential to transmit a virus to other people, with viruses like Ebola having exceptionally high viral loads and common colds having lower ones.
The research group used mathematical models with an artificial intelligence component to investigate previously published clinical data and discovered that successful SARS-CoV-2 variants had an earlier and higher peak in viral load, as well as a shorter duration of infection. They also found that decreased incubation periods and increased proportions of asymptomatic infections were associated with changes in the evolution patterns of the virus when it mutated.
Iwami and his colleagues suggest that human behavior changes designed to limit transmission have increased selection pressure on the virus, leading SARS-CoV-2 to be transmitted primarily during asymptomatic and pre-symptomatic periods earlier in its infectious cycle. As a result, peak viral load advanced to this period for more effective spread within early pre-symptomatic stages. Scientists emphasize that when evaluating public health strategies for Covid-19 and potentially pandemic-causing pathogens in the future, it is essential to consider how changes in human behavior impact virus evolution patterns.
The study highlights complex interactions between clinical symptoms and human behavior as possible factors driving new coronavirus strains’ evolution. It underscores the importance of understanding how people’s actions influence disease dynamics and informs public health policies aimed at controlling outbreaks effectively.