Investigating the increasing trend of EHEC notifications in Swiss surveillance data

The Federal Office of Public Health (FOPH) detected a significant increase in notified cases of infections with enterohaemorrhagic E. coli (EHEC) since 2014. While EHEC cases increase, the number of cases with haemolytic uraemic syndrome (HUS; a complication of EHEC infections) remained stable. It is hypothesised that at least part of this phenomenon can be explained by the use of multiplex PCR panels for stool diagnostics. These multiplex PCR panels are increasingly offered by Swiss laboratories and are likely replacing traditional stool culture methods in the next future. The aim of this project is to evaluate whether the increasing case notifications are a real epidemiological finding or whether they are due to the (changing) testing behaviour in terms of diagnostic methods used and frequency of testing.

The project consists of two parts:

  • A qualitative survey among staff of diagnostic laboratories in Switzerland to learn about (a) the methods applied for EHEC diagnostics, (b) changes in laboratory methods and (c) their potential impact on Swiss infectious disease surveillance
  • A so-called “positivity study” where the time trend in the proportion of positive tests out of all test performed (=positivity rate) for EHEC is described from 2007 to 2016. Multivariable logistic regression models are used to assess associations between a positive test outcome and the patients’ age group and sex, the laboratory and the year of testing.


Claudia Schmutz

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