25 Years of Surveillance for Legionnaires' Disease in England and Wales: Why No Improvement?

Abstract

The European Surveillance Scheme for Travel Associated Legionnaires’ Disease (EWGLINET) has helped strengthen European national surveillance systems and improve case detection and reporting in travel-associated cases. The guidance and legislation introduced in England and Wales over the past 25 years aims to ensure that all relevant systems are properly installed and maintained and that investigation of these systems (e.g., wet cooling towers) in an outbreak situation is as efficient as possible. These measures are aimed at reducing the absolute number of cases of Legionnaires’ disease. England and Wales’ annual case reports severely underrepresent the true annual incidence of Legionnaires’ disease. The urinary antigen test was introduced in England and Wales in the 1990s and is now the primary diagnostic method for 80% of English and Welsh cases of Legionnaires’ disease. The test is quick and easy to perform and might therefore be enabling countries to detect milder cases of the disease that would otherwise have gone undiagnosed. However, in England and Wales the number of cases has remained relatively constant despite the increasing use of the test. The simple trend of an increasing number of cases of Legionnaires’ disease in England and Wales over the past 25 years masks a more complicated picture. Reporting systems that suffer from underdiagnosis and underreporting are likely to register an increase in case reports (as ascertainment improves) before any actual decrease from improved control and prevention in case numbers is detected.