Virulence it is the ability of a biological agent to produce serious or fatal effects. It is related to its ability to multiply in the infected organism, production of toxins, among other factors.
The virulence of a given agent can be determined by the lethality and severity coefficients:
- Lethality Coefficient: Indicates the percentage of fatal cases of the disease;
- Gravity Coefficient: Indicates the percentage of cases considered serious, according to pre-established criteria.
high virulence it means a high proportion of serious or fatal cases, as in rabies, for example, where every case is fatal.
On the other hand, the measles virus, despite its high infectivity and pathogenicity, has low virulence, since the number of deaths from measles in urban areas is low.
Pathogenicity x Virulence
Pathogenicity it is the capacity of the infectious agent to produce symptoms in a greater or lesser proportion among the infected hosts.
The measles virus has a high pathogenicity, as virtually all those infected show specific signs and symptoms.
The polio virus, on the other hand, has low pathogenicity, since, among those infected, only about 1% develop paralysis.