Pathogenicity vs. Virulence

Virulence

Virulence is a pathogen’s or microbe’s ability to infect or damage a host.

In the context of gene for gene systems, often in plants, virulence refers to a pathogen’s ability to infect a resistant host. In most other contexts, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. The pathogenicity of an organism – its ability to cause disease – is determined by its virulence factors. The noun virulence derives from the adjective virulent. Virulent can describe either disease severity or a pathogen’s infectivity. The word virulent derives from the Latin word virulentus, meaning “a poisoned wound” or “full of poison.”In ecology, virulence is the host’s parasite-induced loss of fitness. Virulence can be understood in terms of proximate causes—those specific traits of the pathogen that help make the host ill—and ultimate causes—the evolutionary pressures that lead to virulent traits occurring in a pathogen strain.