Outbreak is a classification used in epidemiology to describe a small, localized group of people or organisms infected with a disease. Such groups are often confined to a village or a small area. Outbreaks may also refer to epidemics, which affect a region in a country or a group of countries, or pandemics, which describe global disease outbreaks.
When investigating disease outbreaks, the epidemiology profession has developed a number of widely accepted steps. As described by the Centers for Disease Control and Prevention, these include the following:
- Identify the existence of the outbreak: is the group of ill persons normal for the time of year, geographic area, etc.?
- Verify the diagnosis related to the outbreak
- Create a case definition to define who/what is included as a case
- Complete descriptive epidemiology: describe outbreak with respect to time, place, and people
- Develop a hypothesis: what appears to be causing the outbreak?
- Study hypothesis: collect data and perform analysis
- Refine hypothesis and carry out further study
- Develop and implement control and prevention systems
- Release findings to greater community
- Common source (Point source)
- Continuous source