Contagiousness index

The contagiosity index (also contamination quotient or contagion index , from Latin: contagium (infection) and index (indicator)) describes the proportion of a non- immune population in which an infection occurs after contact with a pathogen . It is irrelevant whether the infection also leads to an illness, i.e. an infectious disease , only the penetration and multiplication of the pathogen in the new host is used to calculate the contagiousness index. The contagiousness index is an important parameter in epidemiology for describing the probability with which an individual is infected after contact with a pathogen. In the mathematical description of the spread of an epidemic , the index influences the base reproduction number .

definition

The contagiousness index is a (dimensionless) measure of the infectiousness ( contagiousness ) of a pathogen upon first contact. More precisely, it is calculated as the quotient between infected susceptible and exposed susceptible

{\ displaystyle {\ text {KI}} = {\ frac {\ text {Number of infected recipients}} {\ text {Number of exposed recipients}}}}

.

The proportion of these infected people who also become ill is recorded using the manifestation index. In order to determine the contagiosity index in practice, even in non-sick people, a seroconversion is often examined, which in many pathogens is also clinically silent, i.e. H. can proceed without symptoms of illness; one also speaks here of the silent celebration .

For example, if there is a probability that 60% of the people exposed will be infected, the contagiousness index is 0.6.

Examples of the contagiousness index:

Infectious disease	Contagiousness index of the pathogen (as a measure)
measles	0.98
smallpox	0.95
whooping cough	0.90 (0.8-1.0)
mumps	0.8
typhus	0.50
Scarlet fever	0.10-0.30
rubella	0.15-0.20
diphtheria	0.10-0.20
Bacterial agitation	0.15
Typhus abdominalis	0.50
poliomyelitis	0.001-0.003

literature

Anton Mayr et al .: Medical microbiology, infection and epidemic science. 8th revised edition, Stuttgart 2006, ISBN 978-3830410607 , p. 7ff.

Individual evidence

↑ Wolfgang Kiehl: Infection protection and infection epidemiology. Technical terms - definitions - interpretations. Ed .: Robert Koch Institute, Berlin 2015, ISBN 978-3-89606-258-1 , p. 81, keyword contagion index
^ HW Doerr, WH Gerlich (ed.): Medical Virology. Basics, diagnosis, prevention and therapy of viral diseases. 2nd edition, Thieme, Stuttgart 2010, ISBN 978-3-13-113962-7 p. 549.

[:2-1] Wolfgang Kiehl: Infection protection and infection epidemiology. Technical terms - definitions - interpretations. Ed .: Robert Koch Institute, Berlin 2015, ISBN 978-3-89606-258-1 , p. 81, keyword contagion index

[2] HW Doerr, WH Gerlich (ed.): Medical Virology. Basics, diagnosis, prevention and therapy of viral diseases. 2nd edition, Thieme, Stuttgart 2010, ISBN 978-3-13-113962-7 p. 549.