<unk>  is an infectious disease caused by Legionella species, a pleomorphic, aerobic, catalase-positive, oxidase-positive, non-spore-forming, non-capsulated, motile, Gram-negative bacteria. The majority of cases of<unk>  are reported between the Summer and early Fall (between June and October). Approximately 8,000-18,000 individuals are hospitalized annually in the USA for Legionnaires' disease with a case fatality rate ranging between 10% to 35%.<unk>  may be classified into three types based upon the affected organ systems and the clinical presentation: pulmonary infection (Legionnaires' disease), extrapulmonary infection, and Pontiac fever. Legionella is usually transmitted by aerosol droplets when individuals breathe in contaminated mist or vapor (e.g. whirlpool spa, river, cruise ships, cooling towers, air conditioners, water supply systems). L. pneumophila usually invades host cells and replicates intracellularly. In Legionnaires' disease, the majority of exposed patients do not develop any symptoms. Patients who develop clinical manifestations usually report pneumonia-like symptoms that worsen at 4 to 6 days following onset of symptoms and eventually resolve by day 5 to 10 of symptom-onset. Approximately 1% to 35% of individuals progress to develop Legionnaires'-related complications and death. Complications of Legionnaires' disease include empyema, lung failure, acute kidney injury, endocarditis, neurological disease, septic shock, and multi-organ failure. The prognosis is generally good for healthy patients, but patients with co-morbidities are at higher risk of developing complications and death. In contrast, Pontiac fever has a high attack rate but is associated with mild flu-like symptoms that resolve within 1 to 2 days and is almost always self-limited without any complications. The most important risk factor in the development of<unk>  is recent exposure to either aerosolized water or contaminated water. Other risk factors include old age, concomitant lung disease, active smoking status, and immunosuppression. Urine antigen testing in the first-line diagnostic method. Culture of the lower respiratory secretion is the gold standard for the detection of Legionella and diagnosis of Legionnaires' disease. Imaging may also be indicated among patients with Legionnaires' disease. Pharmacologic medical therapy is indicated in Legionnaires' disease, but not in Pontiac fever. The preferred regimens for both mild and moderate-to-severe Legionnaires' disease include either azithromycin or a fluoroquinolone. Patients who develop<unk> -related complications may require other or additional pharmacologic agents. There is no vaccine against<unk> , and antibiotic prophylaxis is not effective.
Legionellosis
Brucellosis
Shigellosis
Bartonellosis
Salmonellosis
Listeriosis
Leptospirosis
Campylobacteriosis