Outbreak is a term used in
epidemiology to describe an occurrence of
disease
greater than would otherwise be expected at 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
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 hypothesis (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:
- 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, small pox, 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
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