Legionnaires' disease outbreak investigation toolbox

When to conduct an analytical study

The primary reason to investigate a Legionella outbreak is to stop the outbreak and prevent new cases, however, the results of investigations can also increase our knowledge of the disease and also serve to evaluate the surveillance system. Ahead of an analytical study, the necessary resources need to be discussed and agreed at an early stage. The impact upon critical functions and arrangements for maintaining resilience should be considered and planned for. Consultation or collaboration with specialist divisions or with external centres of expertise is also advisable where information on microbiological, environmental or other highly technical matters is needed.

Further considerations where an analytical study might be needed include:

• A large number of affected persons
• A high level of public or media concern
• An unknown source or an unknown mode of disease transmission
• Suggestions that new risk factors have been identified
• An outbreak linked to an event of national or international significance
• An outbreak of particular interest to national surveillance
• An outbreak which may be related to standards of institutional care
• Where there is uncertainty and a need for new knowledge