Legionnaires' disease

Legionnaires' disease
SynonymsLegionellosis,[1] legion fever
Legionella pneumophila 01.jpg
Transmission electron microscopy image of L. pneumophila, responsible for over 90% of Legionnaires' disease cases[2]
SpecialtyInfectious disease, pulmonology
SymptomsCough, shortness of breath, fever, muscle pains, headaches[3]
Usual onset2–10 days after exposure[3]
CausesBacteria of the Legionella type (spread by contaminated mist)[4][5]
Risk factorsOlder age, history of smoking, chronic lung disease, poor immune function[6]
Diagnostic methodUrinary antigen test, sputum culture[7]
PreventionGood maintenance of water systems[8]
Prognosis10% risk of death[9]
Frequency~13,000 severe cases a year (US)[10]

Legionnaires' disease, also known as legionellosis, is a form of atypical pneumonia caused by any type of Legionella bacteria.[4] Signs and symptoms include cough, shortness of breath, high fever, muscle pains, and headaches.[3] Nausea, vomiting, and diarrhea may also occur.[1] This often begins 2-10 days after exposure.[3]

The bacterium is found naturally in fresh water.[5] It can contaminate hot water tanks, hot tubs, and cooling towers of large air conditioners.[5] It is usually spread by breathing in mist that contains the bacteria.[5] It can also occur when contaminated water is aspirated.[5] It typically does not spread directly between people, and most people who are exposed do not become infected.[5] Risk factors for infection include older age, a history of smoking, chronic lung disease, and poor immune function.[6] Those with severe pneumonia and those with pneumonia and a recent travel history should be tested for the disease.[11] Diagnosis is by a urinary antigen test and sputum culture.[7]

No vaccine is available.[8] Prevention depends on good maintenance of water systems.[8] Treatment of Legionnaires' disease is with antibiotics.[9] Recommended agents include fluoroquinolones, azithromycin, or doxycycline.[12] Hospitalization is often required.[11] About 10% of those who are infected die.[9]

The number of cases that occur globally is not known.[1] Legionnaires' disease is the cause of an estimated 2-9% of pneumonia cases that are acquired outside of hospital.[1] An estimated 8,000 to 18,000 cases a year in the United States require hospitalization.[10] Outbreaks of disease account for a minority of cases.[1][13] While it can occur any time of the year, it is more common in the summer and fall.[10] The disease is named after the outbreak where it was first identified, at a 1976 American Legion convention in Philadelphia.[14]

Signs and symptoms

The length of time between exposure to the bacteria and the appearance of symptoms is generally 2-10 days, but can rarely extend to as long as 20 days.[15] For the general population, among those exposed, between 0.1 and 5.0% develop the disease, while among those in hospital, between 0.4 and 14% develop the disease.[15]

Those with Legionnaires' disease usually have fever, chills, and a cough, which may be dry or may produce sputum. Almost all experience fever, while around half have cough with sputum, and one-third cough up blood or bloody sputum. Some also have muscle aches, headache, tiredness, loss of appetite, loss of coordination (ataxia), chest pain, or diarrhea and vomiting.[16] Up to half of those with Legionnaires' disease have gastrointestinal symptoms, and almost half have neurological symptoms,[15] including confusion and impaired cognition.[17] "Relative bradycardia" may also be present, which is low or low-normal heart rate despite the presence of a fever.[18]

Laboratory tests may show that kidney functions, liver functions, and electrolyte levels are abnormal, which may include low sodium in the blood. Chest X-rays often show pneumonia with consolidation in the bottom portion of both lungs. Distinguishing Legionnaires' disease from other types of pneumonia by symptoms or radiologic findings alone is difficult; other tests are required for definitive diagnosis.

Persons with Pontiac fever experience fever and muscle aches without pneumonia. They generally recover in 2-5 days without treatment. For Pontiac fever, the time between exposure and symptoms is generally a few hours to 2 days.

Other Languages
العربية: داء الفيالقة
български: Легионелоза
čeština: Legionelóza
Deutsch: Legionellose
español: Legionelosis
Esperanto: Legiana malsano
euskara: Legionelosi
français: Légionellose
galego: Lexionelose
íslenska: Hermannaveiki
italiano: Legionellosi
қазақша: Легионеллез
lietuvių: Legioneliozė
Nederlands: Legionellose
norsk nynorsk: Legionærsjukdom
русский: Легионеллёз
Simple English: Legionnaires' disease
slovenščina: Legioneloza
українська: Легіонельоз
Tiếng Việt: Bệnh Lê dương
中文: 军团病