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Further investigations and actions

Linking associated cases

Reviewing the surveillance form and other local records can identify other cases with common exposures in the recent past. Sources, such as cooling towers, can disperse legionellae intermittently as an ongoing source, rather than a point source, so cases can occur over a period of weeks.

If there is a cluster of cases in your area, the Director of Public Health and Regional Epidemiologist should also be informed.

Once the surveillance form has been faxed to the Centre for Infections, they will check to see if there have been any other cases across the country associated with any of the places visited by your case. The Centre for Infections will also be able to pursue any overseas connections with the relevant authorities (through the Department of Health).


You will need to liaise with the local environmental health department who may:

  • Visit and inspect suspect sites:
    • Check the cleaning and maintenance records of any risk systems such as air conditioning, spa pools, showers
    • Take water samples from these systems
    • Assess whether they feel it is safe for a facility to continue open pending the result of tests or recommend taking it out of use pending results, or
    • Consider closing down the potential source if the risk justified immediate closure.
    • Recommend the use of specialist water engineers to undertake remedial action

Closure of the facility will clearly stop the public risk, but will involve the owner in financial and possibly reputational loss, so if the decision to close is incorrect legal redress may be sought.

A number of companies advertise as being able to give specialist advice on legionella and water systems

In buildings with complex plumbing systems like hotels, legionellae can multiply in the hot and cold water systems and an aerosol can be created when the water from a tap hits the basin. It is thus worth sampling the hot and cold taps as well as the shower head and air conditioning. Organisations/hotels can be signposted to HPA website for information on the disease and how it can be prevented

Lastly, the patient's home water systems can also be sampled. It is quite possible for legionellae to multiply in the water system or shower head during the two weeks he was on holiday.


Although most cases are sporadic and no source is identified, Legionnaires' disease can lead to media interest and some public concern. Therefore it useful to seek specialist advice from the communications team and draft a media release so it is ready should there be media enquiries about the case.

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