outbreak

Outbreak is a term used in epidemiology to describe an occurrence of disease greater than would otherwise be expected in a particular time and place. It may be small and localized group or impact upon thousands of people across an entire continent. Two linked cases of a rare infectious disease may be sufficient to constitute an outbreak. 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

There are several outbreak patterns, which can be useful in identifying the transmission method or source, and predicting the future rate of infection. Each has a distinctive epidemic curve, or histogram of case infections and deaths.^[2]

• Common source - All victims acquire the infection from the same source (e.g. a contaminated water source).^[3]
  • Continuous source - Common source outbreak where the exposure occurs over multiple incubation periods.
  • Point source - Common source outbreak where the exposure occurs in less than one incubation period^[4]
• Propagated - Transmission occurs from person to person.^[5]

Outbreaks can also be:

• Behavioral risk related (e.g., sexually transmitted diseases, increased risk due to malnutrition)^[6]
• Zoonotic - The infectious agent is endemic to an animal population.

patterns of occurence are:

• epidemic- a communicable disease, such as influenza, measles, mumps, pneumonia, colds, small pox found permanently in a particular region or population.

• endemic- when this disease is found to infect "a lot of" people at the same time and may spread through one or several community.

• pandemic- occurs when the epidemic spreads across the world.

Outbreak legislation

Outbreak legislation is still in its infancy and not many countries have had a direct and complete set of the provisions ^{[7], [8]}. However, some countries do manage the outbreaks using relevant acts, such as public health law ^[9].

Notes

Look up outbreak in Wiktionary, the free dictionary.

1. ^ EXCITE | Epidemiology in the Classroom | Outbreak Steps
2. ^ http://ccnmtl.columbia.edu/projects/epiville/study5d.html
3. ^ http://www.cdc.gov/excite/library/glossary.htm#outbreakcommonsource
4. ^ http://www.cdc.gov/excite/library/glossary.htm#outbreakpointsource
5. ^ http://www.cdc.gov/excite/library/glossary.htm#outbreakpropagated
6. ^ http://www.cdc.gov/doc.do/id/0900f3ec802272e6
7. ^ Bioterrorism Training and Curriculum Development Program. "Outbreak Law". http://library.scahec.net/view/product/32. Retrieved 2 August 2008. 
8. ^ Star Publications. "‘Outbreak actions protected by law’". http://thestar.com.my/news/story.asp?file=/2008/7/16/courts/21834412&sec=courts. Retrieved 2 August 2008. 
9. ^ The State of Queensland Government. "Legislation and Powers of Entry". http://www.health.qld.gov.au/dengue/managing_outbreaks/legislation.asp. Retrieved 2 August 2008. 

External links

• Outbreak Alerts Resource for breaking news on outbreaks of communicable diseases.