10.2A: Occurrence of a Disease
- Page ID
- 11600
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- Recognize the steps taken by epidemiologists when investigating disease outbreaks
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 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 endemics that affect a particular place or group, epidemics that affect a region in a country or a group of countries, and pandemics that describe global disease outbreaks.
The epidemiology profession has developed a number of widely accepted steps when investigating disease outbreaks. As described by the Centers for Disease Control and Prevention, these include the following:
- Verify the diagnosis related to the outbreak.
- Identify the existence of the outbreak (if the group of ill persons is 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.
- Develop a hypothesis (if there appears to be a cause for 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.
There are several outbreak patterns that can be useful in identifying the transmission method or source and predicting the future rate of infection.
- Common source – All victims acquire the infection from the same source (e.g. a contaminated water supply).
- 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.
- Propagated – Transmission occurs from person to person.
Each has a distinctive epidemic curve, or histogram of case infections and deaths.
Outbreaks can also be:
- Behavioral risk related (e.g. sexually transmitted diseases, increased risk due to malnutrition)
- Zoonotic – The infectious agent is endemic to an animal population.
Key Points
- Outbreaks may also refer to endemics that affect a particular place or group, epidemics that affect a region in a country or a group of countries, or pandemics that describe global disease outbreaks.
- The epidemiology profession has developed a number of widely accepted steps to investigate a disease occurrence.
- Outbreak patterns, which can be useful in identifying the transmission method or source, and predicting the future rate of infection include common source, continuous source, point source, and propagated source.
- Outbreaks can be behavioral risk related (e.g., sexually transmitted diseases, increased risk due to malnutrition) or zoonotic (e.g. the infectious agent is endemic to an animal population ).
Key Terms
- outbreak: A term used in epidemiology to describe an occurrence of disease greater than would otherwise be expected at a particular time and place.
- epidemic: A widespread disease that affects many individuals in a population.
- pandemic: A disease that hits a wide geographical area and affects a large proportion of the population.