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: a 15-point plan for reducing the risk from Legionella

The risk of Legionnaires' disease can be minimised. Hoteliers and other accommodation owners are recommended to follow the 15-point plan for reducing the risk from Legionella:

1. Have at least one named appointed competent person or a WSG responsible for Legionella control.

2. Ensure the named persons have sufficient training and experience to be able to carry out their role competently and other staff are trained to be aware of the importance of their role in controlling Legionella.

3. Ensure that the source water quality meets the requirements of the EU Drinking Water Directive (Council Directive 98/83/EC) by:

• ensuring that the water supply is continuous (intermittent supplies result in depressurisation of water supply pipework which is likely to result in the release of nutrients (biofilms, scale and corrosion) into the system) and that cold water is kept cold at all times. It should be maintained at temperatures below 25°C (ideally below 20°C) throughout the system to all outlets (this may not be possible when the ambient temperature is high, but every effort should be made to ensure that cold water entering a building and in storage remains as cold as possible).

• checking that there are appropriate backflow protection devices where there are connections from the drinking water system to non-potable water systems (such as fire suppression systems) and or equipment and that these have been checked on an annual basis.

4. Inspect the inside of cold water tanks at least once per year and disinfect with 50 mg/I chlorine and clean if they contain a deposit or are otherwise dirty.

5. Keep hot water hot and circulating at all times: at least 50°C at the outlets (too hot to put hands into for more than a few seconds) throughout the entire hot water system (ensure there are hot water warning signs so users are aware of the scalding risk).

6. Run all taps and showers in guest rooms and other areas for several minutes to draw through water (until it reaches the temperatures stated in points 3 and 4 (or target biocide levels where target water temperatures cannot be achieved)) at least once a week if rooms are unoccupied and always prior to occupation.

7. Keep showerheads, hoses and taps clean and free from scale and biofilm.

8. Clean, drain and disinfect water heaters (calorifiers) once per year.

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

10. Clean and disinfect all water treatment filters regularly as directed by the manufacturer, at least every one to three months. Note POU filters should not be replaced if removed but a new one fitted according to the manufacturer’s instructions.

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

12. Clean and disinfect cooling towers and associated pack and pipes used in evaporative air conditioning systems regularly — at least twice per year.

13. Ensure that when carrying out system modifications or new installations they do not create pipework with intermittent or no water flow, and disinfect the system following any work.

14. If there is a spa pool (also known as hot tubs, whirlpool spas and spa baths) ensure that:

• it is continuously treated with 3-5 mg/I chlorine or bromine and the levels and pH (7.0—7.6) are monitored at least three times per day including at the beginning of each day;

• any adverse monitoring results have been appropriately dealt with in a timely manner;

Legionella testing has been carried out by an accredited laboratory;

• at least half of the water is replaced each day;

• sand filters are backwashed daily after the last user has left the pool;

• the whole system is cleaned and disinfected once per week.

15. Daily records are kept of all water treatment readings, such as temperature, pH and chorine concentrations and ensure they are checked regularly by the manager as being satisfactory.

Further advice about specific controls should be sought from experts in this field. They can carry out a full risk assessment of the accommodation. Your local public health authorities can advise you further.

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