Microbiology
Virulence
The degree of pathogenicity of a microorganism—how much damage it causes to a host. Highly virulent pathogens cause severe disease; low-virulence pathogens cause mild or no symptoms.
Biological Context
Virulence is an evolved trait balancing pathogen interests: more virulent strains exploit hosts more intensely but may kill them before transmission. The evolution of virulence depends on transmission mode, host immunity, and whether multiple pathogen strains coinfect the same host.