Alternative Names legionella pneumophilia pneumonia
Definition Legionnaires' disease is a mild to severe pneumonia caused by bacteria. Outbreaks of Legionnaires' disease are the result of exposure to water contaminated with the bacteria. Exposure can come from shower heads, taps, drinking water, aerosol mists and cooling towers.
What is going on in the body? There are probably several ways that people are exposed to the bacteria that cause Legionnaires' disease. The most common is by breathing in the bacteria from contaminated aerosol mists or from contaminated drinking water. Another is by direct entry of the bacteria into the lungs. The bacteria grow in the small airways of the lung.
The Legionella bacteria can also cause infections outside the lung. These are called extrapulmonary infections and these infections result from the bacteria spreading from the lung into the bloodstream or lymph system. The most common site of infection outside of the lungs is the heart.
What are the signs and symptoms of the infection? The symptoms begin after an incubation period of 2 to 10 days. Symptoms include:
fever
cough
shortness of breath
malaise or fatigue
myalgias, or muscle pains
headache
chest pain
The mild cough may produce slightly blood-streaked sputum, or spit. Diarrhoea occurs in 10 to 20 percent (10% to 20%) of people. Some have vomiting and abdominal pain. There can be neurologic symptoms other than headache. Fever can be high with shaking chills. Low blood sodium is associated with Legionella pneumonia and can cause mental changes and other problems.
Legionella pneumonia can be persistent. It can last for several weeks to several months, if not treated. People can have persistent lung symptoms including fever, cough, chest pain and fatigue.
Legionella pneumophilia has been associated with a flu-like illness called Pontiac fever. This is acute and self-limited. It causes fever, chills, headache, malaise, myalgias, cough, nausea and dizziness. There are no signs or symptoms of pneumonia.
What are the causes and risks of the infection? The cause is exposure to Legionella-contaminated water. The bacteria are found in rivers, lakes, hot water tanks, cooling towers and institutional water supplies, etc. There is controversy about some sources. The disease is more common in humid areas.
Those at highest risk for the infection are people with compromised (weakened or damaged) immune systems, the elderly, and those with chronic lung disease. People on dialysis and those receiving chemotherapy are at risk.
What can be done to prevent the infection? Complete sterilisation of Legionella from water supplies is not practical. It is likely not necessary. Methods of sterilisation for reducing Legionella include super heating and flushing water supplies. Ultraviolet light exposure of outgoing water is effective. Ionisation units with copper silver also work. Hyperchlorination is not used. It is expensive and there are concerns about side effects.
Facilities and hospitals that care for those with compromised immune systems should monitor water supplies. Contamination should be treated. Sterilisation of cooling towers or evaporative condensers is not considered necessary or practical. Vaccinations are being developed. They may be used for high-risk individuals.
How is the infection diagnosed? Diagnosis occurs when an individual has pneumonia. An individual's sputum, or spit, can be analysed. This will give a diagnosis. A chest x-ray often shows fluid on the lungs. This is not unique to Legionnaires' disease, however.
Occasionally, bronchoscopy, which is the insertion of a scope down the windpipe into the lungs to get lung samples for evaluation, is necessary to provide a more certain diagnosis. Lung biopsy, CAT scans or other x-rays are not needed.
What are the long-term effects of the infection? Most who have this infection respond well to therapy. Poor treatment can cause scarring, abscess formation, or pockets of pus, and lung compromise. This is usually not severe. Infection outside the lung usually resolves with treatment. Any infection or inflammation in already immunocompromised individuals is serious. Those who have the disease can develop an immunity.
What are the risks to others? This bacterium is not communicable from one person to another. It is passed only by exposure to contaminated water.
What are the treatments for the infection? This bacterium is sensitive to antibiotics. Many people are treated initially in the hospital with an intravenous antibiotic, or antibiotic given through a vein in the forearm or hand. Once an infected individual is stabilised, he or she can take antibiotics by mouth. Improvement usually occurs within a few days. Those who are otherwise healthy should be treated for 2 weeks. Relapse, or a return of the infection, has occurred. Retreatment with the same medications is necessary.
What are the side effects of the treatments? Side effects of antibiotics can include nausea and diarrhoea. Allergic reactions can occur with use of antibiotics.
What happens after treatment for the infection? After treatment individuals should be aware that relapse can occur. Usually permanent lung damage is not a problem. Many can go on with their daily life.
How is the infection monitored? Checking to make sure any lung problems are healed can be done by clinical evaluation, chest x-ray and testing of oxygen levels. Those with emphysema, or other lung diseases, and those with weak immune systems need to be followed closely.
Author: Thomas Fisher, MD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
