Prognosis and Outcome

About the Disease

Legionnaires' disease is a severe, often lethal, form of pneumonia. It's caused by the bacterium Legionella pneumophila found in both potable and nonpotable water systems. Each year, an estimated 10,000 to 18,000 people are infected with the Legionella bacteria in the United States.

It is not uncommon for patients with Legionnaires' disease to be admitted to the intensive care unit. Some will suffer long-term impaired health-related quality of life.  A study of outbreak survivors showed persistence of fatigue (75%), neurologic symptoms (66%) and neuromuscular symptoms (63%) in months after an outbreak. See Share Your Story for a first-hand account of the severity of this disease.

What is the prognosis and outcome for patients who have contracted Legionnaires' disease?

If the patient is treated with appropriate antibiotics near the onset of pneumonia, the outcome is excellent, especially if the patient has no underlying illness that compromises his/her immune system. For patients whose immune systems are compromised, including transplant recipients, delay of appropriate therapy can result in prolonged hospitalization, complications, and death.


For those patients who are discharged from the hospital, we have found that many will experience fatigue, loss of energy, and difficulty concentrating for several months after discharge from the hospital. In a long-term study of 122 survivors of Legionnaires' disease in the Netherlands, symptoms of fatigue (75%), neurologic symptoms (such as concentration problems and malaise) (75%), and neuromuscular symptoms (such as joint pain or muscle weakness) (79%) had persisted 17 months later (Lettinga KD, Clin Infect Dis, July 1, 2002). Respiratory tract symptoms were also present, but in lower frequency including cough (48%) and shortness of breath on exertion (38%). It could not be determined whether or not the persistence of these symptoms were due to specifically for Legionnaires' disease or for severe pneumonia, in general.


Serious sequelae, fortunately, are rare. In our experience, most patients will recover completely within one year. If the patients are cigarette smokers, the patients should discontinue smoking.