Infectivity

Short description: Pathogen's ability to infect hosts

In epidemiology, infectivity is the ability of a pathogen to establish an infection. More specifically, infectivity is the extent to which the pathogen can enter, survive, and multiply in a host. It is measured by the ratio of the number of people who become infected to the total number exposed to the pathogen.[1]

Infectivity has been shown to positively correlate with virulence, in plants. This means that as a pathogen's ability to infect a greater number of hosts increases, so does the level of harm it brings to the host.[2]

A pathogen's infectivity is different from its transmissibility, which refers to a pathogen's capacity to pass from one organism to another.[1]

## See also

* Basic reproduction number (basic reproductive rate, basic reproductive ratio, R0, or r nought)

## References

1. ↑ 1.0 1.1 Oxford textbook of global public health (6th ed.). Oxford: Oxford university press. 2015. pp. 1486. ISBN 978-0-19-966175-6.
2. ↑ Stewart, AD; Logsdon, JM; Kelley, SE (April 2005). "An empirical study of the evolution of virulence under both horizontal and vertical transmission". Evolution 59 (4): 730–739. doi:10.1554/03-330. PMID 15926685.

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Clinical research and experimental design

Overview|

* Clinical trial
* Trial protocols
* Adaptive clinical trial
* Academic clinical trials
* Clinical study design

Controlled study
(EBM I to II-1)|

* Randomized controlled trial
* Scientific experiment
* Blind experiment
* Open-label trial

Observational study
(EBM II-2 to II-3)|

* Cross-sectional study vs. Longitudinal study, Ecological study
* Cohort study
* Retrospective
* Prospective
* Case–control study (Nested case–control study)
* Case series
* Case study
* Case report

Measures|

| Occurrence|

Incidence, Cumulative incidence, Prevalence, Point prevalence, Period prevalence

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Association|

Risk difference, Number needed to treat, Number needed to harm, Risk ratio, Relative risk reduction, Odds ratio, Hazard ratio

Population impact|

Attributable fraction among the exposed, Attributable fraction for the population, Preventable fraction among the unexposed, Preventable fraction for the population

Other|

Clinical endpoint, Virulence, Infectivity, Mortality rate, Morbidity, Case fatality rate, Specificity and sensitivity, Likelihood-ratios, Pre- and post-test probability

Trial/test types|

* In vitro
* In vivo
* Animal testing
* Animal testing on non-human primates
* First-in-man study
* Multicenter trial
* Seeding trial
* Vaccine trial

Analysis of clinical trials|

* Risk–benefit ratio
* Systematic review
* Replication
* Meta-analysis
* Intention-to-treat analysis

Interpretation of results|

* Selection bias
* Survivorship bias
* Correlation does not imply causation
* Null result

* Category
* Glossary
* List of topics

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