<unk>  is a form of atypical pneumonia caused by any species of Legionella bacteria, quite often Legionella pneumophila. Signs and symptoms include cough, shortness of breath, high fever, muscle pains, and headaches. Nausea, vomiting, and diarrhea may also occur. This often begins 2–10 days after exposure. A legionellosis is any<unk>  caused by Legionella, including<unk>  (a pneumonia), Pontiac fever (a nonpneumonia illness), and Pittsburgh pneumonia, but<unk>  is the most common, so mentions of legionellosis often refer to<unk> . 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, a history of smoking, chronic lung<unk> , and poor immune function. Those with severe pneumonia and those with pneumonia and a recent travel history should be tested for the<unk> . Diagnosis is by a urinary antigen test and sputum culture. No vaccine is available. Prevention depends on good maintenance of water systems. Treatment of<unk>  is with antibiotics. Recommended agents include fluoroquinolones, azithromycin, or doxycycline. Hospitalization is often required. The fatality rate is around 10% for healthy persons and 25% for those with underlying conditions. The number of cases that occur globally is not known.<unk>  is the cause of an estimated 2–9% of pneumonia cases that are acquired outside of a hospital. An estimated 8,000 to 18,000 cases a year in the United States require hospitalization. Outbreaks of<unk>  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<unk>  is named after the outbreak where it was first identified, at a 1976 American Legion convention in Philadelphia.
Legionnaires' disease
Freshers' flu
Lemierre's syndrome
Boutonneuse fever
Scarlet fever
Bartonellosis
Listeriosis
Metal fume fever