BLV-Legionella-concept - Concept to explore the epidemiology of legionellosis in Switzerland

Legionnaires’ disease is caused by Legionella spp. and is notifiable in Switzerland. Cases reported to the Federal Office of Public Health (FOPH) have increased substantially from around 70 cases in 1999 to 280 cases in 2014. Reasons for this increase could include changes in diagnostic methods, disease awareness, risk factors and climate.

The aim of this project is to identify knowledge gaps with regard to the Swiss surveillance system of legionellosis and afterwards develop study outlines to fill these gaps.

After a literature review, study designs to address the following research questions will be developed: What are the diagnostic procedures employed in a patient with pneumonia presenting in general practice or in hospital? How can clustered cases of Legionnaires’ disease and the source of clustered cases be identified? What is the best procedure to interview notified patients in order to identify risk factors and exposures?

In a second part of this project, a study outline for a so-called positivity study is developed. With this study, changes in positivity rates, defined as the proportion of positive tests out of all tests performed, should be identified. This will help to judge whether the increase, which is observed in the notification data, represents a real increase in the incidence of Legionnaires’ disease in Switzerland or whether it is a consequence of changes in testing practices and other factors.

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