The effect of a large Legionnaires' disease outbreak in Southwest Edinburgh on acute and critical care services

Objective: The largest outbreak of Legionnaires Disease (LD) in the UK for a decade occurred in Edinburgh in June 2012. We describe the clinical and public health management of the outbreak. Setting: Three acute hospitals covering an urban area of similar to 480 000. Methods: Data were collected on confirmed and suspected cases and minutes of the Incident Management Team meetings were reviewed to identify key actions. Results: Over 1600 urine samples and over 600 sputum samples were tested during the outbreak. 61 patients with pneumonia tested positive for Legionella pneumophila serogroup 1 by urinary antigen detection, culture, respiratory PCR or serology. A further 23 patients with pneumonia were treated as suspected cases on clinical and epidemiological grounds but had no microbiological diagnosis. 36% of confirmed and probable cases required critical care admission. Mean ICU length of stay was 11.3 (+/- 7.6) days and mean hospital length of stay for those who were admitted to ICU was 23.0 (+/- 17.2) days. For all hospitalized patients the mean length of stay was 15.7 (+/- 14) days. In total there were four deaths associated with this outbreak giving an overall case fatality of 6.5%. Hospital and critical care mortality was 6.1% and 9.1%, respectively. Conclusions: A significant proportion of patients required prolonged multiple organ support or complex ventilation. Case fatality compared favourably to other recent outbreaks in Europe. Access to rapid diagnostic tests and prompt antibiotic therapy may have mitigated the impact of pre-existing poor health among those affected.