Epidemiology module of practical skills for mbbs student

SECTION – C

OUTBREAK INVESTIGATION

OUTBREAK INVESTIGATION, RESPONSE AND CONTROL

An outbreak is defined as the occurrence of an illness in a community, clearly in excess of the expected numbers. Usually an outbreak is limited to a small focal area. When an outbreak covers a larger geographic area and has more than one focal point, it is termed as an epidemic.

Outbreaks are defined differently for different VPDs. For diphtheria, polio, neonatal tetanus or JE, even a single case is an outbreak, whereas for measles and pertussis, a sudden increase in the number of cases is an outbreak. Refer to GoI guidelines for surveillance and outbreak response for AFP and Measles.

SOURCE: Field Guide: Measles Surveillance and Outbreak Investigation, New Delhi, Government of India, 2006, (http://www.npsuindia.org/download/Measles%20Guide.pdf)

Field Guide: Surveillance of Acute Flaccid Paralysis, New Delhi, Government of India, 2005,

(http://www.npspindia.org/download/Redbook.pdf)
Warning signs of an impending outbreak are:

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  ƒ Clustering of cases or deaths in time and/or space
  
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  ƒ Occurrence of two or more epidemiologically linked cases of meningitis or measles
  
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  ƒ Shifting in the age distribution of cases
  

Investigation of an outbreak helps to:

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  ƒ control and limit its spread to other areas
  
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  ƒ ascertain its etiology and understand why it occurred
  
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  ƒ identify high risk areas and groups
  
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  ƒ assess how prevention strategies can be strengthened to reduce or eliminate the risk of future outbreaks