Legionnaires' disease

Legionnaires' disease
SynonymsLegionellosis,[1] legion fever
PMC5258191 cureus-0008-00000000937-i01.png
Chest X-ray of a severe case of legionellosis upon admission to the emergency department.
SpecialtyInfectious disease, pulmonology
SymptomsCough, shortness of breath, fever, muscle pains, headaches[2]
Usual onset2–10 days after exposure[2]
CausesBacteria of the Legionella type (spread by contaminated mist)[3][4]
Risk factorsOlder age, history of smoking, chronic lung disease, poor immune function[5]
Diagnostic methodUrinary antigen test, sputum culture[6]
PreventionGood maintenance of water systems[7]
Prognosis10% risk of death[8]
Frequency~13,000 severe cases a year (US)[9]

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

The bacterium is found naturally in fresh water.[4] It can contaminate hot water tanks, hot tubs, and cooling towers of large air conditioners.[4] It is usually spread by breathing in mist that contains the bacteria.[4] It can also occur when contaminated water is aspirated.[4] It typically does not spread directly between people, and most people who are exposed do not become infected.[4] Risk factors for infection include older age, a history of smoking, chronic lung disease, and poor immune function.[5] Those with severe pneumonia and those with pneumonia and a recent travel history should be tested for the disease.[10] Diagnosis is by a urinary antigen test and sputum culture.[6]

No vaccine is available.[7] Prevention depends on good maintenance of water systems.[7] Treatment of Legionnaires' disease is with antibiotics.[8] Recommended agents include fluoroquinolones, azithromycin, or doxycycline.[11] Hospitalization is often required.[10] About 10% of those who are infected die.[8]

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.[9] Outbreaks of disease account for a minority of cases.[1][12] While it can occur any time of the year, it is more common in the summer and fall.[9] The disease is named after the outbreak where it was first identified, at a 1976 American Legion convention in Philadelphia.[13]

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.[14] 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.[14]

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.[15] Up to half of those with Legionnaires' disease have gastrointestinal symptoms, and almost half have neurological symptoms,[14] including confusion and impaired cognition.[16] "Relative bradycardia" may also be present, which is low or low-normal heart rate despite the presence of a fever.[17]

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