Legionellosis
| Legionnaires' disease | |
|---|---|
| Synonyms | legionellosis, Legion fever |
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|
| Transmission electron microscopy image of L. pneumophila, responsible for over 90% of Legionnaires' disease cases | |
| Classification and external resources | |
| Specialty | Infectious disease, pulmonology |
| ICD-10 | A48.1, A48.2 |
| ICD-9-CM | 482.84 |
| DiseasesDB | 7366 |
| MedlinePlus | 000616 |
| eMedicine | med/1273 |
| MeSH | D007876 |
| Orphanet | 549 |
Legionnaires' disease is a form of atypical pneumonia caused by any type of Legionella bacteria. Signs and symptoms include cough, shortness of breath, high fever, muscle pains, and headaches. Nausea, vomiting, and diarrhea may also occur. This often begins two to ten days after being exposed.
The bacterium is found naturally in fresh water. It can contaminate hot water tanks, hot tubs, and cooling towers of large air conditioners. It is usually spread by breathing in mist that contains the bacteria. It can also occur when contaminated water is aspirated. It typically does not spread directly between people and most people who are exposed do not become infected. Risk factors for infection include older age, history of smoking, chronic lung disease, and poor immune function. It is recommended that those with severe pneumonia and those with pneumonia and a recent travel history be tested for the disease. Diagnosis is by a urinary antigen test and sputum culture.
There is no vaccine. Prevention depends on good maintenance of water systems. Treatment of Legionnaires' disease is with antibiotics. Recommended agents include fluoroquinolones, azithromycin, or doxycycline. Hospitalization is often required. About 10% of those who are infected die.
The number of cases that occur globally is not known. It is estimated that Legionnaires' disease is the cause of between two and nine percent of pneumonia cases that occur in the community. There are an estimated 8,000 to 18,000 cases a year in the United States that require hospitalization.Outbreaks of disease account for a minority of cases. While it can occur any time of the year it is more common in the summer and fall. The disease is named after the outbreak where it was first identified, the 1976 American Legion convention in Philadelphia.
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