Legionella spp. are common environmental bacteria, living in fresh water. They are also known to cultivate in man-made water reservoirs such as cooling towers or shower heads. Infection may lead to legionellosis, a group of diseases ranging from a mild, flu-like illness (Pontiac fever), pulmonary distress to potentially fatal pneumonia, known as Legionnaires’ disease. The burden of disease due to Legionella spp. is unknown. Only high-income countries with well-functioning health systems maintain infectious disease surveillance systems that include Legionella infections. In Switzerland, cases of legionellosis must be reported to the Federal Office of Public Health (FOPH) since 1988. Ever since, number of notifications steadily increased, and more than doubled in the last 15 years.
We conduct a series of studies focusing on the infection pathway from exposure to patient to disease notification in order to better understand the Legionella epidemiology in Switzerland. A first study, a so-called positivity study investigates the proportion of positive cases to the number of diagnostic tests performed for Legionella spp. between 2007 and 2016. The results show a strong increase in testing frequency among diagnostic laboratories while case numbers increased proportionally. The cause of the increase in testing is unclear and testing behaviour is probably different across Swiss regions.
A second study investigates the health systems context comprising scoping literature on guidelines, recommendations and legal regulations of prevention and control, diagnostic pathway, surveillance and outbreak detection of Legionnaires’ disease.
A third exploration of physicians’ management of pneumonia; and patients’ illness experience and care seeking generates actual diagnostic pathways among care providers to identify a case of Legionnaires’ disease. The study among patients aims at investigating the patients’ experience and perceived burden and causes of Legionnaires’ disease. It further acts as a pilot study for a subsequent fourth study to explore the risk factors and exposure sites for contracting Legionnaires’ disease in Switzerland.