Legionnaires’ disease is a form of atypical pneumonia caused by any type of Legionella bacteria.
Epidemiology
Legionnaires’ disease incidence (no. cases/100,000 population) by sex and age group, New York, New York, USA, 2002–2011. | Farnham, A., Alleyne, L., Cimini, D., & Balter, S. (2014). Legionnaires’ disease incidence and risk factors, New York, New York, USA, 2002-2011. Emerging infectious diseases, 20(11), 1795–1802. doi:10.3201/eid2011.131872
Transmission:
Man-made water reservoirs:
Showerheads and sink faucets
Hot tubs that aren’t drained after each use
Decorative fountains and water features
Hot water tanks and heaters
Large plumbing systems
No person-to-person transmission
Aetiology
Risk factors:
Old age
Smoking
Chronic lung disease
Poor immune function
Cause:
Legionella pneumophila(> 90% cases)
Others: L. longbeachae, L. feeleii, L. micdadei, L. anisa
Transmission electron microscopy image of L. pneumophila, responsible for over 90% of Legionnaires’ disease cases | CDC (PHIL #1187) – CDC Public Health Image Library., Public Domain, https://commons.wikimedia.org/w/index.php?curid=841034
Clinical features
Incubation period: 2-10 days
Common symptoms:
Fever (almost all case)
Chills (1⁄2 cases)
Dry/productive cough (1⁄3 cases), shortness of breath
Muscle pains
Headaches
Other symptoms:
Gastrointestinal symptoms (1⁄2 cases)
Diarrhoea
Neurological symptoms (1⁄2 cases): Confusion and impaired cognition
Relative bradycardia
Low/low-normal heart rate despite the presence of a fever
Legionnaires’ disease is very similar to other types of pneumonia (lung infection), with symptoms that include cough, shortness of breath, fever, muscle aches, and headaches.
Diagnosis
Lab investigations:
Urinary antigen test (DIAGNOSTIC)
Sputum culture
Imaging:
Imaging studies of 42-year-old man with severe pneumonia caused by Legionella pneumophila serogroup 11, showing lobar consolidation of the left lower lung lobe, with an air-bronchogram within the homogeneous airspace consolidation. Consensual mild pleural effusion was documented by a chest radiograph (A) and high-resolution computed tomography (B). A week after hospital admission, repeat high-resolution computerized tomography of the chest showed extensive and homogeneous consolidation of left upper and lower lobes, accompanied by bilateral ground-glass opacities (C and D). | Antonella Grottola; Comments to Author , Fabio Forghieri, Marisa Meacci, Anna Fabio, Lorena Pozzi, Patrizia Marchegiano, Mauro Codeluppi, Monica Morselli, Leonardo Potenza, Ambra Paolini, Valeria Coluccio, Mario Luppi, Fabio Rumpianesi, and Monica Pecorari – Emerging Infectious Diseases, http://wwwnc.cdc.gov/eid/article/18/11/12-0216-f1.htm, Public Domain, https://commons.wikimedia.org/w/index.php?curid=22731973
