Legionnaires' disease is a form of pneumonia caused by any type of Legionella bacteria. Over 90% of cases are caused by Legionella pneumophila.
The length of time between exposure to the bacteria and the appearance of symptoms is generally two to ten days. It can be as much as 20 days. People with Legionnaires' usually have fever, chills, and a cough. Some also have muscle aches, headache, tiredness, loss of appetite, diarrhea or vomiting.
People of any age may have Legionnaires' disease. It is most common in middle aged and older people.