Legionnaires disease

Legionnaires' disease is a potentially fatal form of pneumonia which can affect anybody, but which principally affects those who are susceptible because of age, illness, immunosupression, smoking etc. It is caused by the bacterium Legionella pneumophila and related bacteria. Legionella bacteria can also cause less serious illnesses which are not fatal or permanently debilitating. The collective term used to cover the group of diseases caused by legionella bacteria is legionellosis. There are 200-250 reported cases in the United Kingdom each year.


Spread and Infection

It is normally contracted by inhaling legionella bacteria, either in tiny droplets of water (aerosols), or in droplet nuclei (the particles left after the water has evaporated), deep into the lungs. There is evidence that inhaling legionella bacteria following ingestion of contaminated water by susceptible individuals may also contract the disease. Person-to-person spread of the disease has not been documented. Initial symptoms of Legionnaires' disease include high fever, chills, headache and muscle pain. Patients may develop a dry cough and most suffer difficulty with breathing. About one third of patients infected also develop diarrhoea or vomiting and about half become confused or delirious. Legionnaires' disease can be treated effectively with appropriate antibiotics.

L. pneumophila is also responsible for a short feverish form of the illness without pneumonia, known as Pontiac fever. Its incubation period is typically between two to three days. Another species of legionella, L. micadadei, is responsible for a similar form of the illness without pneumonia called Lochgoilhead fever after an outbreak in Lochgoilhead, Scotland. The incubation period can be up to nine days. A high percentage of those exposed to this agent tend to be affected. However, there have been no recorded deaths associated with either Pontiac or Lochgoilhead fevers.


Exposure risk

A reasonably foreseeable risk of exposure to legionella bacteria exists in:

  • water systems incorporating a cooling tower;
  • water systems incorporating an evaporative condenser;
  • hot and cold water systems; and
  • other plant and systems containing water which is likely to exceed 20 degrees and which may release a spray or aerosol (ie. a cloud of droplets and/or droplet nuclei) during operation or when being maintained

Legislation

In order to deal with cooling towers and evaporative condensers all premises that have one of these items must notify the Local Authority under the notification of Cooling Towers and Evaporative Condensers Regulations 1992. This includes premises where the enforcing authority is the Health and Safety Executive.
Control of legionella: investigation of outbreaks (and single cases) of legionellosis from water systems incorporating cooling towers and evaporative condensers
Health & Safety Executive / Local Authorities Enforcement Liaison Committee (HELA)
Local Authority Circular Subject: Legionnaires disease LAC Number: 46/4
Open Government Status: Open Revised: February 2002 Review date: February 2005


Inspection of cooling towers

Premises located in the Royal Borough of Kensington and Chelsea , which have a cooling tower, or evaporative condenser, enforced by the Royal Borough of Kensington and Chelsea's Directorate of Environmental Health, are visited once or twice a year, depending on a risk assessment carried out by the inspecting officer. The tower (or evaporative condenser) and associated plant is thoroughly inspected together with supporting documentation about water treatment, monitoring, cleaning and communication which is kept by the tower operator.

The risk from hot and cold water systems and other plant liable to release a spray or aerosol e.g. humidifiers, spa baths, pools, car washes, indoor fountains and water features is assessed during general inspection of the premises. The hazard and risk from legionella is incorporated into the general risk assessed health and safety programme operated by the Royal Borough of Kensington and Chelsea.

However outbreaks of legionnaires disease do still occasionally occur but there has not been an outbreak in the Royal Borough of Kensington and Chelsea since that at the Science Museum (Health and Safety Executive enforced) in 1989. The Borough has a documented procedure to deal with an outbreak which would involve setting up an "outbreak control team" in co-operation with NHS Kensington and Chelsea, and other relevant experts.

Legionnaires disease represents a real threat of serious disease and death. The Council, through the above measures is actively working to minimise this risk.


Further information