Pathogen evolution is the study of how microorganisms such as bacteria, viruses, parasites, and fungi evolve over time. This evolution can lead to the development of drug resistance, changes in virulence, and adaptations to new hosts or environments. Researchers in this field investigate mechanisms of genetic change, factors driving evolutionary processes, and the impact of pathogen evolution on human health, agriculture, and ecosystems. Studying pathogen evolution is critical for understanding and combating infectious diseases and developing strategies for disease control and prevention.