2.2 Potential outbreak source locations

Identifying potential outbreak source locations should be regarded as a minimum requirement for the use of GIS for Legionnaires' disease outbreak investigation. By establishing the potential sources of an outbreak, GIS can be used to conduct comparative analysis to assess the relative likelihood of each potential source being responsible (see section 1.3 Comparing potential outbreak sources).

Potential outbreak source locations will be represented as point features within a GIS and care should be taken to ensure a high level of spatial precision in recording these locations. In the outbreaks described in section 3. Literature review, cooling towers and other aerosol emitting facilities have been identified as the responsible sources, but premises such as swimming pools and car washes have also been considered in relation to Legionnaires' disease. Data sourcing for facilities such as cooling towers will vary between nations. In a number of countries it is a statutory requirement to register a cooling tower with a particular administrative body, either at local, regional or national level; however in other countries it is not. Cooling tower registers may be out-of-date, incomplete and there may also be a number of unregistered premises. It is likely that some field reconnaissance may be required to quality-check cooling tower registers and also to identify other potential outbreak sources.

Considerations for a cross-border outbreak: It should be possible for nations to share the locations of potential outbreak sources in the event of a cross border outbreak. In a number of countries it is a statutory requirement to register a cooling tower with a particular administrative body; indeed it would be highly desirable in a European context for this to be a statutory requirement across all member states. Establishing and routinely maintaining such data, in a common format would no doubt assist greatly with any investigation into an Legionnaires' disease outbreak. Attempting to collate information on potential sources at the beginning of an outbreak investigation is a time consuming process, therefore having a resource available that already contains those likely sources would speed up the investigation process and could potentially save lives. However, the cost of maintaining the potential source locations, so they are relevant during any outbreak may be high; and public health teams having sufficient remit to collect the data in first place, and then centrally store the information so that it is coherently available when required, needs to be resolved/clarified.