Following COVID-19, the world faces the risk of further zoonotic diseases. These will result from humankind’s continued changing of natural ecosystems. To prepare for future pandemics, it is important to continue research into infectious diseases that could affect people and wildlife alike. This means focusing on pathogens that have the capacity to infect multiple species.
Both viral and bacterial emerging infectious diseases are unpredictable. They also tend to lead to a high morbidity and they have the potential to trigger a rapid growth of cases.
According to a new review article published in the journal eLife, there is a pressing need for a multidisciplinary research framework to explore links between evolved tolerance to pathogens and their spill over into humans.
While immune strategies, ecology and pathogen prevalence all play crucial roles in allowing spill over, the authors report that studying these various factors in isolation is “far from ideal” given the complex interactions involved.
The types of inquiries that the authors discuss include considering the evolutionary basis of pathogen tolerance in reservoir hosts. This means why does a pathogen move from one animal to another, without causing adverse effects, but then causes serve illnesses when moving to the next host?
Of interest is the process of long-term co-evolution, that will allow reservoir hosts to modulate immunity. At the same time, such hosts can evolve tolerance to zoonotic pathogens, increasing their circulation and infectious period.
This process could additionally create a genetically diverse pathogen pool, such as allowing more mutations and genetic exchanges between circulating strains. The effect of this could be to harbour rare alive-on-arrival variants with extended infectivity to new hosts (what the researchers refer to as ‘spill over’).
This phenomenon has been corroborated by recent analyses and mathematical models “indicating that the number of zoonotic viruses with spillover risk might increase proportionally with the total number.”
The paper suggests that the different factors need to be jointly studied to explain the patterns and processes of pathogen prevalence and infection outcomes in the wild. In addition to being a general concept, this approach is relevant to the present crisis created by the COVID-19 pandemic and emerging infections.
Furthermore, this holistic strategy further provides a newer understanding of other important aspects of public health, such as infectious disease control.
The research article is titled: ‘Evolution of pathogen tolerance and emerging infections: A missing experimental paradigm’.
