Background Legionella pneumonia (LP) has been reported in a number of outbreaks in the UK. It has significant implications for public health as outbreaks require investigation to identify a responsible source. An outbreak of LP occurred in the Stoke-on-Trent area of North Staffordshire in July 2012. This is an analysis of the clinical cases reported and subsequent public health enquiry.

Method Retrospective review of case records, pathology and radiology. Data was collated on clinical and biochemical features, microbiology and clinical outcome. Results of the public health enquiry were sourced from the local Health Protection Agency (HPA).

Results 20 patients were confirmed to have LP. 13 male, 7 female. Mean age was 65 years. 50% were ex-smokers. 70% had at least two co-morbidities requiring treatment. 3 were immunosuppressed on longterm steroids. Only 1 patient reported foreign travel in the preceding month. Clinical, biochemical and radiological findings are shown in Table 1. Urinary legionella antigen was detected in all patients. Sputum PCR for legionella pneumophilia was positive in 8 cases and identified a single strain present in all samples (ST1268). Mean length of stay was 8.9 days. 6 patients (30%) required admission to intensive care for respiratory support; 2 were invasively ventilated. 18 patients were discharged home, 2 died. 65% had follow-up chest xrays showing improvement or resolution of consolidation. All cases were from the Stoke area. The HPA investigation detected the same legionella pneumophilia strain in a display spa pool at a retail unit, as found in the sputum. As no other tested sites were found to have this strain, it is very likely this was the origin of the local outbreak. All cases had visited the retail unit prior to their hospital admission.

Conclusion LP remains a possible diagnosis in any case of community acquired pneumonia. This outbreak is a reminder that patients do not always present following the classic travel history. The diagnosis needs to be considered and vigilance in microbiological testing is necessary to identify potential cases.