Kentucky Cabinet for Health and Family Services (Banner Imagery) - Go to home page


Division of Epidemiology
275 East Main Street
Frankfort, KY  40621
502-564-3418 or 3261  

What is legionellosis?

Legionellosis is an infection caused by the bacterium Legionella pneumophila. Legionnaires’ disease acquired its name in 1976 after an outbreak of pneumonia occurred among a group of individuals attending an American Legion Convention in Philadelphia. The bacterium that causes the illness was named Legionella. This disease can take two distinct forms:

Legionnaires’ disease, a serious form of infection that includes pneumonia.
Pontiac fever, a milder form of infection.

Who is at risk for legionellosis?

Anyone of any age can contract legionellosis. Approximately 8,000 to 18,000 people get Legionnaires’ disease in the United States each year. However, most often the disease affects middle-aged and older persons. Outbreaks of the disease usually receive major media attention, but most often this disease occurs as a single, isolated case. When outbreaks do occur they are usually in the summer or early fall, but cases occur year-round. About 5% – 30% of people who get Legionnaires’ disease die. You may be at risk for legionellosis if you:

Smoke cigarettes.
Have chronic lung disease.
Have diseases such as cancer, kidney failure that requires dialysis, diabetes, or AIDS, that suppress your immune system.
Take drugs that suppress the immune system.
Pontiac fever occurs usually in individuals who are otherwise healthy.

How is legionellosis spread?

Several outbreaks of legionellosis have occurred after individuals have breathed mists that come from a water source (air conditioning cooling towers, whirlpool spas, showers) that were contaminated with Legionella bacteria. Individuals may be exposed to these mists in homes, workplaces, hospitals, or other public places. Legionellosis is not passed from person to person, and there is no evidence that individuals can become infected from auto air conditioners or household window air conditioners.

The Legionella organism can be found in many types of water systems. But the bacteria multiply best in warm, stagnant water that is 90° – 105° F. It has been found in certain plumbing systems, hot water tanks, cooling towers and evaporative condensers of large air-conditioning systems, and whirlpool spas. Legionellosis is believed to occur worldwide.

What are the symptoms of legionellosis?

The time between patient’s exposure to the bacterium and the onset of illness for Legionnaires' disease is 2 to 10 days. Individuals with Legionnaires’ disease usually will experience any or all of the following signs or symptoms:

Cough (can be dry or produce sputum).
Muscle aches.
Weakness or tiredness.
Loss of appetite.
Occasionally diarrhea.
Possible kidney malfunctioning.
Onset for Pontiac fever is shorter generally a few hours to 2 days. Individuals with Pontiac fever experience any or all of the following signs or symptoms:

Muscle aches.
NO pneumonia.

How is legionellosis diagnosed?

The only way to know if you are infected with legionellosis is by having specific laboratory test done in relation to clinical signs and symptoms of the disease by your health care provider. It is hard to distinguish Legionnaires’ disease from other types of pneumonia by symptoms. Tests that are usually completed for diagnosis of legionellosis may include all or any of the following:

Renal function.
Chest x-rays.
Laboratory test that detect Legionella are usually completed on any or all of the following:

Sputum (bacteria).
Urine (antigens), easiest and fastest identification of the disease.
Blood samples (antibody) done 3 to 6 weeks apart.

What is the treatment for legionellosis?

Antibiotic treatment is recommended for individuals with Legionnaires’ disease. In very serious cases another drug may be used in addition to the antibiotic.

Pontiac fever requires no specific treatment, individuals usually recover in 2 to 5 days without treatment.

How can legionellosis be prevented?

Improved design and maintenance of cooling towers and plumbing systems to limit the growth and spread of Legionella organisms are the bases of legionellosis prevention.

The Centers for Disease Control and Prevention and health department investigators seek to identify the source of disease transmission and recommend appropriate prevention and control measures, such as decontamination of the water source during outbreaks. On-going research will likely identify additional prevention strategies.


Last Updated 12/16/2008