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Disease outbreaks

A disease outbreak is the occurrence of cases of disease in excess of what would normally be expected in a defined community, geographical area or season. An outbreak may occur in a restricted geographical area, or may extend over several countries. It may last for a few days or weeks, or for several years.

A single case of a communicable disease long absent from a population, or caused by an agent (e.g. bacterium or virus) not previously recognized in that community or area, or the emergence of a previously unknown disease, may also constitute an outbreak and should be reported and investigated.

RELATED SITES

- Epidemic and Pandemic Alert and Response (EPR)

FACT SHEETS

- Rift Valley fever
- Monkeypox
- Nipah virus
- Plague

RELATED LINKS

- Global Outbreak Alert and Response Network

FEATURES

- Online Q&A: How does WHO get information about disease outbreaks in the affected countries?


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