virulence
Quick Summary
Virulence refers to the degree of pathogenicity of a microorganism, or its ability to overcome host defenses and cause disease. It is a measure of how severe an infection caused by a pathogen is. This can include the relative capacity of a bacterium or virus to cause damage or illness.1
Factors contributing to virulence include the production of toxins, enzymes that break down host tissues, and substances that interfere with normal cell functions. The invasiveness of a pathogen, its ability to penetrate and spread through tissues, also contributes to its virulence.23
Virulence is not an absolute quality but is evaluated in relation to the host's resistance. A pathogen's virulence can be assessed by determining the dose required to cause a typical reaction in a certain percentage of hosts.4
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diseaseHost resistanceCommonly, for example, virulence of an infective agent is determined experimentally by inoculating groups of hosts with graded doses of the agent and determining, by interpolation, the dose that produces a typical reaction in 50 percent of the host individuals inoculated. This dose is called the median effective…
Read MoreCommonly, for example, virulence of an infective agent is determined experimentally by inoculating groups of hosts with graded doses of the agent and determining, by interpolation, the dose that produces a typical reaction in 50 percent of the host individuals inoculated. This dose is called the median effective…
Read More- animal diseaseInfectious and noninfectious diseases
…to cause infection—is known as virulence. The capacity of a virulent organism to cause infection is influenced both by the characteristics of the organism and by the ability of the host to repel the invasion and to prevent injury. A pathogen may be virulent for one host but not for…
Read More…to cause infection—is known as virulence. The capacity of a virulent organism to cause infection is influenced both by the characteristics of the organism and by the ability of the host to repel the invasion and to prevent injury. A pathogen may be virulent for one host but not for…
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human diseaseInvasiveness and virulenceIn general, virulence is the degree of toxicity or the injury-producing potential of a microorganism. The words virulence and pathogenicity are often used interchangeably. The virulence of bacteria usually relates to their capability of producing a powerful exotoxin or endotoxin. Invasiveness also adds to an organism’s virulence…
Read MoreIn general, virulence is the degree of toxicity or the injury-producing potential of a microorganism. The words virulence and pathogenicity are often used interchangeably. The virulence of bacteria usually relates to their capability of producing a powerful exotoxin or endotoxin. Invasiveness also adds to an organism’s virulence…
Read More- Darwinian medicineDeveloping applications
…coexistence but in levels of virulence (ability to damage tissues) shaped to maximize the rate of pathogen spread. Virulence often depends on the route of transmission. For instance, respiratory viruses severe enough to keep victims in bed are likely to be displaced by less-severe strains whose victims are mobile enough…
Read More…coexistence but in levels of virulence (ability to damage tissues) shaped to maximize the rate of pathogen spread. Virulence often depends on the route of transmission. For instance, respiratory viruses severe enough to keep victims in bed are likely to be displaced by less-severe strains whose victims are mobile enough…
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plant diseasePathogenesis and saprogenesis…their ability to infect, is virulence. Many different properties of a pathogen contribute to its ability to spread through and to destroy the tissue. Among these virulence factors are toxins that kill cells, enzymes that destroy cell walls, extracellular polysaccharides that block the passage of fluid through the plant system,…
Read More…their ability to infect, is virulence. Many different properties of a pathogen contribute to its ability to spread through and to destroy the tissue. Among these virulence factors are toxins that kill cells, enzymes that destroy cell walls, extracellular polysaccharides that block the passage of fluid through the plant system,…
Read More