Legionnaire's disease is caused by the intracellular bacterium Legionella pneumophilia. It typically colonizes water tanks and hence questions may hint at air-conditioning systems or foreign holidays. Person-to-person transmission is not seen

Features

• flu-like symptoms including fever (present in > 95% of patients)
• dry cough
• confusion
• relative bradycardia

Investigations

• FBC - lymphopaenia
• U&E - hyponatraemia
• LFT - deranged liver function tests
• CXR - pleural effusion: seen in around 30% of patients, multifocal bilateral consolidation
• Diagnosis - urinary antigen

Management

• treat with erythromycin/clarithromycin