Legionnaires' disease outbreak investigation toolbox

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Information for Owners and Managers of Hotels and Other Accommodation Sites: Minimising the Risk


Around 870 cases of travel associated legionnaires' disease in European residents were reported to the European surveillance scheme in 2008. The risk from Legionnaires' disease can be reduced by careful attention to a number of simple measures. This page contains summary information for site owners and hotel managers and also provides links to other relevant resources.

What is Legionnaires' disease?

An uncommon form of pneumonia (lung infection) from which approximately 5-15% of those that become ill will die. It is caused by Legionella bacteria. These bacteria can also cause less serious illness. The infected person usually takes between 2-10 days to develop symptoms (typically five to six days but very rarely some cases may take two to three weeks to develop symptoms).

The illness usually starts with a fever, chills, headache and muscle pain. This is followed by a dry cough and breathing difficulties that may progress to severe pneumonia. About 30% of those infected will also have diarrhoea or vomiting and about 50% become confused or delirious.

Accurate diagnosis requires specific laboratory tests that often are not done until the guests have returned home.

How is Legionnaires' disease caught?

Legionnaires' disease is caught by breathing in air containing the Legionella bacteria. The bacteria are in small, invisible water droplets (aerosols). Aerosols can be formed whenever fine droplets are generated from contaminated water. In hotels with no effective legionella control programme this may be from running a tap or shower, flushing a toilet, or from bubbles rising through water in a spa pool. The bacteria, which also live naturally in the environment, can live and multiply in water at temperatures of 20°C to 45°C and high numbers occur in inadequately maintained man-made water systems.

Is the hotel the source of infection?

When travel associated cases of Legionnaires' disease are forwarded by ECDC to the country of infection, the report never implies that the patient got their infection from the hotel at which they stayed because they could have got their infection from a variety of different places. However, when it is discovered that two or more cases have stayed at the same accommodation, especially within a short period of time (such as within two to four weeks), it increases the probability that the source might be linked to it. In this situation, urgent investigations at the accommodation site are expected to be carried out that will help to answer this question.

Most hotels are aware of the risk of Legionnaires' disease and have taken measures to prevent this risk as much as possible.

Where are the risk areas in a hotel?

Wherever water droplets (aerosols) can be created there is a risk of infection e.g.:

• Showers and taps

• Spa baths and whirlpool baths

• Turkish baths and saunas

• Cooling towers and evaporative condensers used for air conditioning, even if situated on the roof or in the grounds

• Ornamental fountains, particularly indoors

• Humidified food displays

Where can Legionella bacteria multiply?

• Hot and cold water tanks / cisterns

• Warm water between 20°C and 45°C

• Pipes with little or no water flow (this includes unoccupied rooms)

• In slime (biofilm) and dirt on pipe and tank surfaces

• Rubber and natural fibres in washers and seals

• Water heaters and hot water storage tanks

• Scale in pipes, showers and taps.

These situations and conditions encourage the growth of Legionella bacteria and increase the risk of infection to hotel guests and staff.

Reducing the risk - the 14 point checklist

The risk of Legionnaires' disease can be minimised. Any hotel that does not have an active programme to control the growth of Legionella bacteria is negligent in ensuring the safety of their guests. This programme should include the following:

1. Have one named person responsible for legionella control

2. Ensure the named person is trained in control of Legionella and other staffs are trained to be aware of the importance of their role in controlling Legionella

3. Keep hot water hot and circulating at all times: 50°C - 60°C (too hot to put hands into for more than a few seconds)

4. Keep cold water cold at all times. It should be maintained at temperatures below 25°C

5. Run all taps and showers in guest rooms for several minutes at least once a week if they are unoccupied and always prior to occupation

6. Keep shower heads and taps clean and free from scale

7. Clean and disinfect cooling towers and associated pipes used in air conditioning systems regularly - at least twice a year

8. Clean and disinfect water heaters (calorifiers) once a year

9. Disinfect the hot water system with high level (50mg/l) chlorine for 2-4 hours after work on water heaters and before the beginning of every season

10. Clean and disinfect all water filters regularly - every one to three months

11. Inspect water storage tanks, cooling towers and visible pipe work monthly. Ensure that all coverings are intact and firmly in place

12. Inspect the inside of cold water tanks at least once a year and disinfect with 50mg/l chlorine and clean if containing a deposit or otherwise dirty

13. Ensure that system modifications or new installations do not create pipe work with intermittent or no water flow

14. If there is a spa pool (also known as whirlpool spas, "Jacuzzis", spa baths) ensures that:

• It is continuously treated with 2-3mg/l chlorine or bromine and the levels are monitored at least three times a day

• At least half of the water is replaced each day

• Sand filters are backwashed daily

• The whole system is cleaned and disinfected once a week

• Daily records of all water treatment readings such as temperature and chlorine concentrations are kept and ensure they are checked regularly by the manager.

Further advice about specific controls should be sought from experts in this field who can carry out a full risk assessment of the hotel site. Your local public health authorities may be able to recommend a good source of advice.

Legionella testing

Testing for Legionella is a useful tool but only on condition that it is carried out by trained personnel. Water samples should be examined by laboratories accredited for testing water for Legionella bacteria (e.g. by UKAS or equivalent national bodies elsewhere). A negative test result does not necessarily mean that the hotel is clear of Legionella or that there is no risk.

How do I find out more?

There is more advice available in the European guidelines for control and prevention of travel associated Legionnaires' disease which is available in the ECDC website at http://ecdc.europa.eu/en/activities/surveillance/ELDSNet/Pages/Index.aspx