Outbreak is an infectious disease that affects a larger number of people than would normally be expected in a given community or geographical area at a particular time and season. These diseases can spread directly between humans, from animals to human beings, or via insect vectors. Most of these outbreaks can be attributed to human behaviours that facilitate their spread. Infectious agents that spread through these pathways can be zoonotic, endemic or epidemic in nature.
In the case of a zoonotic pathogen, the disease is endemic in animal populations but has been transmitted to people by their contact with animal tissue (skin, meat, milk, etc). An endemic infection can become epidemic or pandemic when it infects a larger number of individuals than usual.
The investigation of an outbreak requires a broad range of epidemiological approaches. The preferred study design in an outbreak is a case-control study when it is possible to match cases with healthy controls who share a set of characteristics, such as exposures, that are related to the cause of the outbreak.
This type of analysis can explore the role of specific factors in fostering an outbreak. However, because outbreak investigations are often urgent and resource-constrained, more general control and prevention measures can be implemented from the outset. For example, suspect foods can be removed from the market or sick people who commercially work in manufacturing or processing food products may be restricted from their activities. Providing health education in schools or on ocean liners could also be important preventive measures.
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