A team of researchers from Nagoya University (Japan) has recently uncovered that human behavior, such as confinements and isolation measures, can impact the evolution of new strains of SARS-CoV-2, the virus that causes Covid-19. The study, published in Nature Communications, provides valuable insights into the relationship between people’s behavior and disease-causing agents.
Viruses are living organisms that evolve over time, with those that have survival advantages becoming dominant. Human behavior plays a crucial role in this process as it alters the environment in which the virus operates. By isolating sick individuals and using lockdowns to control outbreaks, humans can influence the evolution of the virus in different ways. Predicting these changes is essential for developing adaptive treatments and interventions.
The concept of viral charge is an important aspect of this interaction. It 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 is related to the potential to transmit a virus to other people, with viruses like Ebola having an exceptionally high viral load while common colds have a low one.
The research group led by Professor Shingo Iwami used mathematical models with an artificial intelligence component to analyze previously published clinical data. They 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. The researchers also found that changes such as decreased incubation period and higher proportion of asymptomatic infections recorded as the virus mutated affected virus evolution patterns.
Iwami and his colleagues suggest that human behavior changes designed to limit transmission put selection pressure on the virus, causing SARS-CoV-2 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 during early pre-symptomatic stages. Scientists emphasize that when evaluating public health strategies in response to Covid-19 or potentially pandemic-causing pathogens in the future, it is necessary to consider how changes in human behavior impact virus evolution patterns.
Overall, this study highlights how human behavior can significantly influence disease evolution patterns and underscores the importance of considering these factors when developing public health strategies for infectious diseases like Covid