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.

Outbreak Investigation

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^[1]:

• Verify the diagnosis related to the outbreak
• Identify the existence of the outbreak: is the group of ill persons normal for the time of year, geographic area, etc.?
• 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

Types

• Common source (Point source)
• Propagated
• Continuous source
• Zoonotic

Notes

1. ^ http://www.cdc.gov/excite/classroom/outbreak/steps.htm