Legionnaires' disease outbreak investigation toolbox

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Name of Local Public Health team DATE

Legionella Infections in LOCATION


Legionnaires' disease has been diagnosed in a number of patients in LOCATION.

We are writing to you because there is a chance that you/a member of your family may have been infected with this disease. Should you experience symptoms, you should seek medical attention promptly, so that you can receive appropriate and effective treatment.

Legionnaire's disease is an uncommon form of pneumonia caused by a type of bacterium that is found in the environment. It causes disease when it is spread through the air as a spray or vapour from a water source and droplets are inhaled. It cannot be spread from one person to another.

The symptoms of Legionnaires' disease include a 'flu-like' illness with muscle aches, tiredness, headaches, dry cough and fever, leading on to pneumonia. Sometimes diarrhoea occurs and patients may suffer from confusion. It can be treated with antibiotics. You should seek medical attention if you have experienced the symptoms outlined in the past couple of weeks.

The period between infection and symptoms developing (the incubation period) ranges from 2 to 19 days. In rare cases some people may develop symptoms as late as three weeks after exposure.

If you experience the symptoms outlined above please contact your doctor and take a copy of this letter with you.

Additional information

Legionnaires' disease is pneumonia, caused by the bacterium Legionella pneumophila. The majority of cases are reported as single (isolated) cases but outbreaks can occur. Some 5000 cases are reported annually across the EU and EEA/EFTA countries. All ages can be affected, but it mainly affects people over 50 years of age, and generally men more than women and more often, smokers.

It cannot be passed from person to person. Outbreaks may have a source of infection in common but most cases are 'sporadic' i.e. with no links to a common source or strain of the Legionella bacteria.

Legionella bacteria are widely distributed in the environment. Systems linked to outbreaks have included: cooling towers; evaporative condensers; hot and cold water systems; spa pools; humidifiers in food display cabinets; effluent treatment plants; air scrubbers.

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