Human disease and the evolution of pathogen virulence

Area of Science:

• Evolutionary biology
• Pathogen dynamics
• Disease ecology

Background:

• Theoretical models of host-parasite co-evolution often oversimplify by not accounting for the link between host pathology and pathogen transmission.
• Previous generalizations about co-evolutionary endpoints (commensalism vs. increased parasitism) may be inaccurate due to this omission.

Purpose of the Study:

• To challenge existing a priori generalizations in host-parasite co-evolution theory.
• To highlight the critical role of the empirical relationship between host pathology and pathogen transmission.
• To classify human diseases based on how pathology influences transmission.

Main Methods:

• Review and synthesis of existing knowledge on host-pathogen interactions.
• Classification framework development based on pathology-transmission dynamics.
• Analysis of human disease examples.

Main Results:

• Pathogen virulence is shaped by natural selection based on whether host pathology facilitates or impedes transmission.
• Diseases where pathology enhances transmission are predicted to favor increased pathogen virulence.
• Diseases where pathology hinders transmission are predicted to favor decreased pathogen virulence.

Conclusions:

• Accurate predictions of host-parasite co-evolution require empirical data on pathology-transmission links.
• The virulence of a pathogen is contingent on its transmission strategy and the host's pathological response.
• Classifying diseases by pathology's role in transmission offers a more nuanced understanding of co-evolutionary dynamics.