Host-Microbe Interactions and Pathogenesis 30). Pathogenici…
Host-Microbe Interactions and Pathogenesis 30). Pathogenicity is the ability of a pathogen to cause disease; virulence describes the degree or extent of disease that a pathogen causes. Whereas pathogenicity is an all-or-nothing term, virulence varies, may depend on both pathogen and host features, and may evolve over time. To endure over time, a pathogen’s ability to break down defenses and live within a host must be balanced with the ability to transmit to others. A highly-virulent pathogen which is transmitted person-to-person and causes high-mortality outbreaks that rapidly kill or debilitate hosts usually remains geographically isolated and causes short-lived outbreaks. Over time, this pathogen may evolve into one which does not kill victims right away, thus increasing the time available for transmission.