BAG - Food- und Waterborne-Themen - Research on the epidemiology of food- and waterborne diseases in Switzerland

Financed by the Federal Office of Public Health (FOPH) various studies are conducted to elucidate specific topics of interest to the office in the fields of prevention, control and evidence-based guideline development related to the management of food- and waterborne pathogens in Switzerland:

(1) Testing frequency and positivity rates of Legionella
Surveillance data show an increasing trend in legionellosis cases since the beginning of reporting in 1988. A first, strong increase after the year 2000 can be explained by the introduction of a simple and non-invasive test method (urinary antigen test) most likely leading to increased case detection. However, the expected flattening of the curve some years after the introduction of this new test method did not occur; contrary, there was again a steep increase in case numbers in 2015.
The current study aims at investigating if the observed increase is the result of an increase in legionellosis cases in the population (increasing incidence) or of a changing diagnostic behaviour by physicians and/or laboratories (leading to increased case detection). We analyse data from selected diagnostic laboratories in Switzerland on all tests conducted for Legionella spp. from 2007 to 2016. Leading questions are: Did test numbers increase? Did the proportion of positive tests out of all tests performed change? What are determinants for trends observed?

(2)  Understanding the current epidemiology of hepatitis A in Switzerland
Hepatitis A notifications are decreasing since 1990. However, the last detailed analyses of surveillance databases used data up until 2004. A contemporary analysis of notification data is needed considering that the information gathered through national surveillance also informs policy makers to plan prevention measures and to adapt vaccination recommendations.
We analyse notification data on hepatitis A from 1988 to 2016. Considering the interest of the Federal Advisory Commission on Immunisation we especially explore information on vaccination status and exposure.

(3)  Analysis of notification data on "statistic of reports on laboratory findings"
Since the implementation of the revised Epidemics Act in Switzerland in January 2016, information on the number of tests performed has to be reported as an annual statistic for a number of notifiable diseases by diagnostic laboratories, additional to individual case reports. This "statistic of reports on laboratory findings" should help interpreting trends in the number of individual case reports as the latter not only depend on disease frequency in the population but can also be influenced by physicians' awareness for a disease, their case management (diagnostic testing vs. empirical treatment), and by laboratory practices affecting test numbers.
We analyse data from the first two years of reporting of those "statistic of reports on laboratory findings" with special emphasis on the data's usefulness and validity.

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