Legionnaires' disease outbreak investigation toolbox

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Design of a case-control study [1]

Case-control studies

In most outbreaks the population is large or not well defined, and so cohort studies are not feasible. In these instances, you would use the case-control study design. Case-control studies can be matched or unmatched, where matching is used as one way to control confounding by selecting study participants so as to ensure that potential confounding variables (such as age and sex) are evenly distributed in the two groups being compared (refer to Legionnaires' Disease Outbreak Study protocol).

Definition: epidemiological study of persons with the disease (or other outcome variable) of interest and a suitable control group of persons without the disease. Potential relationship of a suspected risk factor or an attribute to the disease is examined by comparing the diseased and non-diseased subjects with regard to how frequently the factor or attribute is present in each of the groups.

  1. BONITA R., BEAGLEHOLE R. & KJELLSTROM T. (2006) Basic Epidemiology World Health Organisation http