Legionnaires' disease is a type of pneumonia. It was named after an
outbreak of severe pneumonia that affected a meeting of the American
Legion in 1976. It is an uncommon but serious disease.
It is actually one of a group of similar diseases collectively known
as legionellosis. The other forms, eg Pontiac Fever and Lochgoilhead
Fever, have similar symptoms but are not as serious as Legionnaires'
disease.
Legionnaires' disease occurs more frequently in men than women. It
usually affects middle-aged or elderly people, and it more commonly
affects smokers or people with other chest problems.
About half the cases of Legionnaires' disease are caught abroad, and
useful advice on travel can be obtained from the European
Working Group for Legionella Infections (EWGLI). The other half are
the result of infections acquired in the UK.
How do people get it?
The agent that causes Legionnaires' disease is a bacterium called Legionella
pneumophilia. People catch Legionnaires' disease by inhaling
small droplets of water suspended in the air, which contain the
bacteria.
Certain conditions increase the risk from legionella:
a suitable temperature for growth, 20 to 45oC;
a source of nutrients for the organism, eg sludge, scale, rust,
algae, and other organic matter;and
a way of creating and spreading breathable droplets, eg the
aerosol created by a cooling tower or spa pool.
However, remember that most people exposed to legionella do not become
ill, and Legionnaires' disease does not spread from person to person.
What are the symptoms?
The symptoms of Legionnaires' disease are similar to those of flu:
high temperature, fever and chills;
cough;
muscle pains; and
headache.
In a bad case there may also be pneumonia, and occasionally diarrhoea
and signs of mental confusion.
Where does it come from?
Legionella bacteria are widespread in nature, mainly living in natural
water systems, eg rivers and ponds. However, the conditions are rarely
right for people to catch the disease from these sources.
Outbreaks of the illness occur from exposure to legionella growing in
purpose-built systems where the water is maintained at a temperature
high enough to encourage growth, eg cooling towers, evaporative
condensers, spa pools, and hot water systems used in all sorts of
premises (work and domestic).
Most community outbreaks in the UK have been linked to installations
such as cooling towers, which can spread droplets of water over a wide
area. These are found as part of air-conditioning and industrial cooling
systems.
Fatal cases of Legionnaires' disease have also been associated with
spa pool demonstrations.
What measures are there to control legionella?
To prevent exposure to the legionella bacteria, you as a dutyholder
must comply with legislation that requires you to manage, maintain and
treat water systems in your premises properly. This will include, but
not be limited to, appropriate water treatment and cleaning regimes.
Remember, legionella can grow in any workplace if the conditions are
right - you do not have to work with microbiological agents, eg in a
laboratory, for exposure to occur. If you are responsible for any of the
water systems described in HSE's Approved Code of Practice (ACoP) and
Guidance "Legionnaires' disease: The control of legionella bacteria
in water systems" (L8) you will need to assess the risk of
employees and others in the workplace contracting Legionnaires' disease.
Copies of L8 can be purchased from HSE
Books. HSE also publishes several free
leaflets and a video explaining legal duties and the control of
legionella in cooling systems and hot/cold water systems available from
HSE Books.
Separate regulations (The Notification of Cooling Towers and
Evaporative Condensers Regulations 1992) require the notification of
cooling towers to your Local
Authority (contact them directly for further information).
What to do if you or an employee has Legionnaires' disease
L8 gives advice on actions to take in the event of finding legionella
in your workplace and also during an outbreak.
The Legionella Working Group
The HSE have established a Legionella working group with the aim of
improving communications between stakeholders and to develop a
consistent approach to Legionella-related plant and
management systems.
If you are responsible for premises inspected by your Local Authority
you should direct any queries about legionella in your workplace to them
initially or try the HSE InfoLine.
The Hazardous Installations Directoriate (HID) has a proactive
inspection programme looking at legionella in cooling towers, further
information on this can be found in their Operating
Plan.
