Symptoms of Legionnaires' disease 

The symptoms of Legionnaires’ disease are initially mild, but usually develop into more serious problems associated with pneumonia.

Symptoms can begin any time from two to 19 days after exposure to the initial infection. However, six to seven days is the most common time between getting the infection and the onset of symptoms (known as the incubation period).

Symptoms usually begin with an initial phase that lasts one to two days, in which you experience flu-like symptoms, such as:

  • mild headaches
  • muscle pain

This is followed by more severe symptoms, including:

  • high temperature (fever), usually 38ºC (100.4ºF) or above
  • more severe muscle pain
  • chills
  • tiredness 
  • changes to your mental state, such as confusion

Once bacteria begin to infect your lungs, you may also experience symptoms of pneumonia, such as:

  • a persistent cough, usually dry at first but as the infection develops you may start coughing up mucus or, rarely, blood
  • shortness of breath
  • chest pains

Some people with Legionnaires’ disease also have symptoms that affect the digestive system, including:

  • feeling sick
  • being sick
  • diarrhoea
  • loss of appetite

When to seek medical advice

If you develop the symptoms above, you should see your GP as soon as possible. In particular, a high temperature is likely to indicate you have an infection of some kind.

Alternatively, you can telephone NHS Direct on 0845 4647 for advice. If you experience problems late at night or early in the morning, you may need to use your local out-of-hours service.

If you have more severe symptoms, such as chest pains and breathing difficulties, seek urgent medical attention.

Page last reviewed: 23/11/2012

Next review due: 23/11/2014