Virulence factor

Virulence Factor

Virulence factors are molecules produced by pathogens (bacteria, viruses, fungi and protozoa) that add to their effectiveness and enable them to achieve the following: colonization of a niche in the host (this includes attachment to cells), immunoevasion, immunosuppression, entry into and exit out of cells (if the pathogen is an intracellular one), and obtaining nutrition from the host.

Pronunciation

Virulence Factor: /vɪˈrʌləns ˈfæktər/

Etymology

The term "virulence" comes from the Latin word "virulentus" meaning "full of poison". The term "factor" comes from the Latin word "factor" meaning "doer, maker".

Related Terms

Pathogen: A bacterium, virus, or other microorganism that can cause disease.
Immunoevasion: The process by which pathogens evade the immune system.
Immunosuppression: Reduction of the activation or efficacy of the immune system.
Intracellular: Located or occurring within a cell or cells.

Function

Virulence factors can contribute to virulence in several ways. They help pathogens enter host cells, evade the host's immune response, and obtain nutrition from the host. Some virulence factors are directly toxic to the host, while others aid in establishing an infection.

Examples

Examples of virulence factors include the toxins produced by bacteria, the capsule found on the outside of bacteria like Streptococcus pneumoniae and Haemophilus influenzae, which prevents phagocytosis, and the enzymes produced by bacteria that can damage the host's cells.

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Virulence factor