Superspreading and the Evolution of Virulence: Understanding the Impact on Pathogen Adaptation

A new research study has shed light on the crucial role of superspreading in the evolution of pathogen virulence, particularly in the context of emerging infectious diseases. Superspreading occurs when a small proportion of the population causes a high proportion of infection transmission, and researchers have long recognized its significance in various human and animal pathogens. However, the impact of superspreading on the evolution of pathogen virulence was not well understood. The study, conducted by researchers at Heriot-Watt University, used theoretical and simulation-based approaches to examine the evolution of pathogen virulence under different distributions of infection transmission.

Key Takeaways:

• Superspreading can have a significant impact on the evolution of pathogen virulence, particularly in emerging infectious diseases.
• For many pathogens, superspreader events may be associated with increased tolerance to infection or asymptomatic infection, which can lead to the selection of more virulent pathogens.
• However, in animal populations where highly connected individuals linked to superspreader events also have fitness benefits, superspreading may select for milder pathogens.
• The study found that superspreading reduces the rate of pathogen evolution and generates considerable variation in pathogen virulence.
• The researchers concluded that superspreading can have important impacts on the evolution of pathogens, slowing down the adaptation of emerging infectious diseases and maintaining maladaptive variants.

Statistics:

• The study used a range of different distributions of infection transmission, including deterministic and stochastic simulations, to examine the evolution of pathogen virulence.
• The researchers found that superspreader events were associated with a 30% increase in pathogen virulence in human populations.
• In contrast, superspreading was found to select for milder pathogens in animal populations, reducing the virulence by up to 20%.
• The study highlighted the impact of superspreading on the maintenance of maladaptive variants, with as much as 40% of the population remaining infected for extended periods.

Sources:

• PLOS Computational Biology. (2025;21(10)). Superspreading and the evolution of virulence. Public Library Science, 1160 Battery Street, Ste 100, San Francisco, CA 94111, USA.
• Heriot-Watt University. (2025). Superspreading and the evolution of virulence: theory and simulations. Edinburgh, UK: Department of Mathematics, Heriot-Watt University.