Legionellosis classification
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] {{AE}]Tarek Nafee, M.D. [2] Ogechukwu Hannah Nnabude, MD
Overview
Legionellosis 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. Legionellosis may also be classified based on the infectious species responsible for the disease.
Classification
Legionellosis may be classified into three types based upon affected organ systems and clinical presentation:
Pulmonary Infection (Legionnaires' Disease)
- Legionnaires' disease may further be classified into:
- Community-acquired Legionnaires' disease (most commonly L. pneumophila)
- Healthcare associated Legionnaires' disease (most commonly L. pneumophila)
- Pittsburgh pneumonia (caused by L. micdadei)
Extrapulmonary Legionella Infection
- The following organ systems may be involved:
- Cutaneous involvement legionellosis
- Legionella encephalopathy
- Disseminated legionella infection
Pontiac Fever
- A mild flu-like infectious disease without pneumonia. It is often distinguished from Legionnaires' disease by clinical features (see table below).
| Characteristic | Legionnaires' disease | Pontiac fever |
| Clinical features | Pneumonia, cough, fever | Flu-like illness (fever, chills, malaise) without pneumonia |
| Radiographic pneumonia | Yes | No |
| Incubation period | 2-14 days after exposure | 24-72 hours after exposure |
| Etiologic agent | Legionella species | Legionella species |
| Attack rate[1] | < 5% | > 90% |
| Isolation of organism | Possible | Never |
| Outcome | Hospitalization common Case-fatality rate: 5-30% |
Hospitalization uncommon Case-fatality rate: 0% |
Microbiological Classification
Legionellosis may also be classified based on the infectious species responsible for the disease. Species of Legionella include: