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You are here: Home / Knowledge / Guidance / Recognising the Symptoms of Legionnaires Disease

What are the Symptoms of Legionnaires’ Disease?

Symptoms of Legionnaires DiseaseBefore the notorious outbreak of Legionnaires’ disease in Philadelphia, USA in 1976, which ultimately led to the discovery of the Legionella bacterium, no one knew what caused the illness that led to the severe pneumonia-like infection that can cause death in the worst-case scenario.

Today however, we have a much better understanding of Legionella bacteria, how they spread and develop, and how they affect people and can potentially make them ill. It can sometimes be difficult to diagnose Legionnaires’ disease to start with, mainly because many of the symptoms are also indicative of influenza or flu.

What are the Symptoms of Legionnaires’ Disease?

So, what are the symptoms? Someone suffering from Legionnaires’ disease is likely to feel feverish and tired in the early stages. They may also suffer muscle aches and pains and get headaches.

As you can see, all these symptoms are also very similar to those of the flu. However, as the infection progresses, it will start to affect the lungs. Since the Legionella bacterium infection causes symptoms like those of pneumonia, anyone affected can expect to develop a cough, shortness of breath and pains in the chest. At this stage, it is vital to seek medical help quickly.

Infection from contaminated aerosols

While legionella cannot be spread from one person to another, it can be caught if mist in the air, referred to as an aerosol, has become contaminated and is then inhaled by someone. Think of the wet spray from a shower, for example, or mist coming out of cooling towers. These are both situations where legionella can easily develop and spread if the maintenance, cleaning, disinfection and sterilisation procedures in place are not good enough to keep bacteria numbers within the control limits set by the Health & Safety Executive (HSE) in their ACOP L8 document.

  • How to test water for Legionella bacteria

How long before symptoms of the disease develop?

The usual incubation time for someone inhaling infected water droplets and developing the first symptoms of the disease is about a week. However, some people fall ill just two or three days later, while for others it might be almost three weeks before they experience symptoms.

Identifying to source of the infection

Using this timeline can help identify the source of the infection when someone has been confirmed to have contracted Legionnaires’ disease. This is important, because the source of the infection must be found so it can be dealt with effectively and so prevent others from falling ill.
Oftentimes, there are clusters of cases that occur and these can help make it easier to identify the common link between them all. In doing so, the source of contamination can be identified and dealt with so no one else falls ill.

Knowing the symptoms of Legionnaires’ disease is very important, particularly if you live or work near cooling towers or use other water-based facilities that could potentially be prone to contamination by Legionella bacteria.

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Further reading

For additional information about Legionella bacteria and Legionnaires’ disease … here

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Useful downloads…

  • HSE ACOP L8 – Control of Legionella
  • HSG274 Part 1 – Evaporative Cooling
  • HSG274 Part 2 – Hot & Cold
  • HSG274 Part 3 – Other Risks
  • Positive Legionella Tests – What To Do?
  • HSG282 – Spa Pools
  • Legionnaires’ – Duty Holders Guide
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