Outbreak

In epidemiology, an outbreak is a sudden increase in occurrences of a disease in a particular time and place. It may affect a 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 United States 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
• Map the spread of the outbreak using Information technology as diagnosis is reported to insurance
• Develop a hypothesis (What appears to be causing the outbreak?)
• Study hypotheses (collect data and perform analysis)
• Refine hypothesis and carry out further study
• Develop and implement control and prevention systems
• Release findings to greater communities

Outbreak debriefing and review has also been recognized as an additional final step and iterative process by the Public Health Agency of Canada.^[2]

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.^[3]

• Common source – All victims acquire the infection from the same source (e.g. a contaminated water supply).^[4]
  • 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^[5]
• Propagated – Transmission occurs from person to person.^[6]

Outbreaks can also be:

• Behavioral risk related (e.g., sexually transmitted diseases, increased risk due to malnutrition)^[7]
• Zoonotic – The infectious agent is endemic to an animal population.

Patterns of occurrence are:

• Endemic – a communicable disease, such as influenza, measles, mumps, pneumonia, colds, smallpox, which is characteristic of a particular place, or among a particular group, or area of interest or activity.
• Epidemic – when this disease is found to infect a significantly larger number of people at the same time than is common at that time, and among that population, and may spread through one or several communities.
• Pandemic – occurs when an epidemic spreads worldwide.

Outbreak legislation

Outbreak legislation is still in its infancy and not many countries have had a direct and complete set of the provisions.^[8][9] However, some countries do manage the outbreaks using relevant acts, such as public health law.^[10]

See also

• 1947 New York City smallpox outbreak
• 1993 Four Corners hantavirus outbreak
• 2003 Midwest monkeypox outbreak
• 2007 Yap Islands zika virus outbreak
• 2014 Democratic Republic of the Congo Ebola virus outbreak
• Super-spreader

References

1. Steps of an Outbreak Investigation, EXCITE | Epidemiology in the Classroom | Outbreak Steps
2. Public Health Agency of Canada. "Canada’s Food-borne Illness Outbreak Response Protocol (FIORP) 2010: To guide a multi-jurisdictional response". Retrieved 22 March 2013.
3. Archived March 19, 2009, at the Wayback Machine.
4. Glossary of Epidemiology Terms, Cdc.gov (2007-04-25). Retrieved on 2010-11-25.
5. Glossary of Epidemiology Terms. Cdc.gov (2007-04-25). Retrieved on 2010-11-25.
6. Glossary of Epidemiology Terms. Cdc.gov (2007-04-25). Retrieved on 2010-11-25.
7. Archived September 28, 2008, at the Wayback Machine.
8. "Bioterrorism Training and Curriculum Development Program". Retrieved 2 August 2008.
9. Star Publications. "‘Outbreak actions protected by law’". Retrieved 2 August 2008.
10. The State of Queensland Government. "Legislation and Powers of Entry". Retrieved 2 August 2008.

External links