LEGIONNAIRES' DISEASE

CONTENTS

WHAT IS LEGIONNAIRES' DISEASE?

Legionnaires' disease is one of a group of diseases collectively known as legionellosis. Others are Pontiac fever and Lochgoilhead fever. Of these infections legionnaires' disease is the most serious.

WHO IS MOST AT RISK?

Those most at risk include smokers, alcoholics and people suffering from cancer, diabetes, chronic respiratory or kidney disease. But healthy people can also be infected. Most reported cases have been in people aged between 40 and 70; men are more likely to be affected than women.

WHERE IS LEGIONELLA FOUND?

Legionella bacteria are widespread in natural sources of water including rivers, streams and ponds and may even be found in soil. They are also found in many recirculating and hot and cold water systems. Outbreaks of legionnaires' disease have occurred in or near large building complexes such as hotels, hospitals, offices and factories. There is no evidence that water systems in domestic homes present any risk.

IF LEGIONELLA IS SO WIDESPREAD WHY AREN'T THERE MORE OUTBREAKS?

Infection is caused by people breathing in water droplets contaminated with legionella bacteria. But for infection to occur a chain of events has to take place and fortunately this does not happen very often. The chain includes:

  • conditions suited to the multiplication of the organism, ie water temperature in the range 20°C to 45°C and the presence of sludge, scale, rust, algae and organic matter to provide nutrient;
  • a means of creating breathable droplets;
  • contact with the droplets by a susceptible person.

Cooling towers, such as those which form part of an air conditioning system, can represent a particular hazard because they readily generate fine water droplets and there is an air current to carry them away. Because they are often located on roof-tops there is a potential for infecting large numbers of people. The bacteria may also colonise hot and cold water systems - showers and spa baths have been associated with infection.

HOW CAN THE RISK BE REDUCED?

Since legionella is widespread in the environment, it cannot be prevented from entering water systems. However, the risk of an outbreak developing can be reduced by taking the following precautions:

Hot and cold water service

  • cisterns and pipe work should be designed so that water is not allowed to stand undisturbed for long periods;
  • cisterns should be well covered to prevent the entry of dirt, debris and vermin, and should be periodically inspected, cleaned and disinfected;
  • water temperatures between 20°C and 45°C should be avoided by insulation of cold water tanks and pipes in warm spaces, and by storing hot water at 60°C and circulating at 50°C. Where there is a risk of scalding for the very old, and young children, thermostatically controlled taps may be needed;
  • only water system fittings and materials which comply with water authority by-laws should be used (certain materials, eg leather, some rubbers and plastics, support the growth of bacteria and should not be used).

Cooling tower

  • cooling towers and their associated water systems need to be well designed, maintained and operated; the fitting of efficient drift eliminators which reduce the escape of spray is especially important;
  • systems should be cleaned and disinfected at least every six months;
  • water should be treated to prevent scale, corrosion and microbiological growth;
  • where reasonably practicable, cooling towers should be replaced with dry cooling systems.

Other water systems

Precautions are necessary wherever water conditions are likely to support the growth of bacteria and there is a means of dispersing droplets, eg commercial spa baths and humidifiers.

WHAT ARE THE LEGAL DUTIES?

The Health and Safety at Work etc Act 1974 and the Control of Substances Hazardous to Health Regulations 1988 both apply. Practical guidance on the legal duties is given in an Approved Code of Practice from the Health and Safety Commission (copies can be obtained by using the attached order form). The Code provides a basic framework of risk management for preventing further outbreaks of the disease. In Scotland, legionellosis is a notifiable disease.

ORDER FORM

Please print and post

Please send me the following HSE books:

The prevention or control of legionellosis (including legionnaires' disease) Approved Code of Practice (L8) 1994, ISBN 0 7176 0457 8 £3.00

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The control of legionellosis, including legionnaires' disease (HS(G)70) 1993, ISBN 0 7176 0451 9 £4.95

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Please debit my Access/Visa Account No:

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(Please note separately the full name and address of the card holder if different from that below)

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NOTIFICATION

With effect from 2 November 1992, all those in control of premises containing wet cooling towers and/or evaporative condensers must notify their local authority Environmental Health Department that they have this equipment.

Notification will help environmental health officers and others to act quickly if an outbreak occurs.

Notification forms are available from Environmental Health Departments.

IF THERE IS AN OUTBREAK WHAT ACTION IS TAKEN?

As soon as an outbreak is suspected a team of specialists, including staff from the local authority Environmental Health Department and the Public Health Laboratory Service, mount an investigation to:

  • identify the source;
  • identify those people likely to be affected;
  • ensure the contaminated water system is treated as quickly as possible.

Investigation has shown that in some years as many as 40% of cases of legionnaires' disease reported in the UK were contracted while abroad.

FURTHER INFORMATION

In addition to the Approved Code of Practice, the Health and Safety Executive has published a booklet, The control of legionellosis, including legionnaires' disease. This contains technical advice on assessing and minimising the risk from exposure to legionella. It reflects the progress of research and experience into the disease since earlier guidance was issued in 1987, and takes account of outbreaks of the disease that have occurred since then. (Copies of the ACOP and booklet can be obtained by using the attached order form). A helpful video, Control of legionella, is also available. For details contact: CFL Vision, PO Box 35, Wetherby, West Yorkshire LS23 7EX. Tel: 01937 541010.

This leaflet is produced by the Health and Safety Executive. HSE priced and free publications are available by mail order from:

HSE Books, PO Box 1999, Sudbury, Suffolk CO10 6FS.

Tel: 01787 881165 Fax: 01787 313995

HSE priced publications are also available from:

Dillons Bookstores and all good booksellers.

For enquiries Tel: 0541 545500, or write to HSE's Information Centre, Broad Lane, Sheffield S3 7HQ.

Fax: 0114 2892333

This leaflet contains notes on good practice which are not compulsory but which you may find helpful in considering what you need to do.

This leaflet may be freely reproduced, except for advertising, endorsement or sale purposes. The information it contains is current at 11/94. Please acknowledge the source as HSE.

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