Legionella Risk Assessments

Where does it come from?

Legionella bacteria are widespread in natural water systems, e.g. 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 water is maintained at a temperature high enough to encourage growth, e.g. cooling towers, evaporative condensers, spa pools, and hot water systems used in all sorts of premises (work and domestic).

The First Known Outbreak of Legionnaires Disease

It is now known that Legionella is fairly common in natural water systems, but that was not always the case. The bacteria wasn’t identified until 1976 when more than 200 people who attended an “American Legion” convention at the Bellevue-Stratford Hotel in the American city of Philadelphia began to report being seriously ill shortly after returning home.

34 would eventually die before the bacteria was identified and the type of pneumonia the victims suffered from was named “legionnaires’ disease” in their honour. It was eventually theorized that the bacteria had thrived in the water of the hotel’s air conditioning system and that the affected people had breathed in contaminated water droplets that had fallen from air conditioning units where water was stored on the roof onto the sidewalk around the hotel.

How do people get it?

People can catch legionnaires’ disease by inhaling small droplets of water, suspended in the air, containing the bacteria. Certain conditions increase the risk from legionella, including:

• water temperature between 20–45 °C, which is suitable for growth
• creating and spreading breathable droplets of water, e.g. aerosol created by a cooling tower, or water outlets
• stored and/or re-circulated water
• a source of nutrients for the organism e.g. presence of sludge, scale or fouling

While most cases of legionnaires’ disease are the result of infections caught in the UK, a number of cases occur abroad.

What are the symptoms?

The symptoms are similar to those of flu, i.e. high temperature, fever and chills, cough, muscle pains and headache. In a severe case, there may also be pneumonia, and occasionally diarrhoea, as well as signs of mental confusion. Legionnaires’ disease is not known to spread from person to person.

In most cases, symptoms develop in 2 to 10 days following exposure to the legionella bacteria. As mentioned, common symptoms include headache, muscle pain and fever. For some people, that is as far as the disease will go. Others, however, will experience a dangerous escalation of symptoms beginning 2 or 3 days after the original onset. Those new, more severe symptoms may include:

• Cough (often with mucus and sometimes blood).
• Respiratory distress in the form of shortness of breath or wheezing.
• An escalating fever perhaps reaching as high as 104F (40C), sometimes higher.
• A heavy sensation in the chest or chest pain.
• Diarrhoea, nausea and/or vomiting.
• Confusion, loss of mental sharpness.
• Infections in other parts of the body besides the lungs.

A less severe form of Legionnaires’ Disease commonly known as “Pontiac Fever” will typically produce similar symptoms but not to any extreme degree. For instance, there is no coughing up blood and no lung infection. Pontiac Fever typically resolves in 2 to 5 days.

When should you see a doctor?

If you are exhibiting any of the above symptoms or have any reason to suspect exposure to legionella bacteria, you should see your doctor immediately for a legionella test. Early detection is critical if you are to avoid it developing into a serious respiratory condition. Keep in mind too that the risk of exposure is more acute for older individuals and smokers.