Contagiousness ( Latin contagiosus - contagious, contagious) - the property of infectious diseases is transmitted from sick people (animals) to healthy susceptible people (animals) by transmitting their pathogen through direct contact or through transmission factors.
The contagiousness index is expressed as a percentage or fraction of a unit; it is determined by counting the number of susceptible (previously not sick and not vaccinated), who became ill with a clinically expressed form of the disease after they contact the source of the pathogen within the epidemic focus.
The concept of "contact" depends on the mechanism of transmission of infection .
The contagiousness index depends on the virulence of the pathogen and the degree of susceptibility of people due to the level of innate immunity, as well as on the availability of conditions for the implementation of the mechanism of transmission of infection. So, yellow fever is not transmitted at all through household items and bed linen, even abundantly moistened with bloody secretions of patients, but for this, a single bite of an infected mosquito Aedes aegypti is enough [1] .
Contagiousness should not be confused with virulence .
Disease Contagiousness Index
- bubonic plague - in the absence of fleas - 0.2, in the presence of fleas Xenopsylla cheopis - one bite of an infected flea;
- typhus - in the absence of lice - practically 0, with bites of infected lice - 0.5;
- malaria - in the absence of mosquitoes - almost 0, in the presence of mosquitoes Anofeles - one bite of an infected mosquito;
- tick-borne encephalitis - in the absence of ticks - practically 0, with bites of infected ticks - 0.5;
- diphtheria , meningococcal infection , brucellosis - 0.2;
- anthrax , typhoid fever , viral hepatitis A - 0.4;
- tularemia , KU – fever - 0.5;
- glanders , melioidosis , psittacosis , cholera - 0.6;
- hemorrhagic fevers - 0.7;
- measles - 0.9 [2] [3] ;
- pulmonary plague - 0.8.
See also
- Virulence
- Pathogenicity
- Infectious diseases
- Infectious dose
Notes
- ↑ Paul de Kreif (de Cruy) . Microbial hunters. Publisher: Astrel, Polygraphizdat, 2012. ISBN 978-5-271-35518-9 , ISBN 978-5-4215-3274-3
- ↑ Measles (Rubeola) - Transmission // CDC
- ↑ Factsheet about measles // European Center for Disease Prevention and Control