About the Project

SNSF project Watussi: Understanding the Drivers of Surgical Site Infection: Investigating and Modeling the Swissnoso Surveillance Data

Within the SSI Surveillance module Swissnoso oversees the nationwide collection of data on select procedures and the associated SSI. Since the inception of this dedicated surveillance in 2009, more than 300’000 procedures have been included and the corresponding patients were followed to ascertain SSIs. Although primarily conceived as a national surveillance system and then used for public reporting starting in 2014, Swissnoso SSI Surveillance is a prime data source for better understanding the epidemiology of SSI.

Here, the research project Watussi – financed by the Swiss National Science Foundation SNSF – seeks to raise the quality of evidence behind future prevention guidelines. For this purpose, the investigators will move from a risk factor analysis for SSI to the collection of additional data – in order to better characterize certain determinants of SSI and their recognition – and, finally, to a mathematical model which will simulate the probability of developing SSI so the investigators can test what may modulate this risk.

Aim 1: Descriptive epidemiology and risk factors for (post-discharge) SSI

In Aim 1, using the Swissnoso SSI Surveillance data, the investigators will determine patient and institution level risk factors for SSI in Switzerland (with a focus on those occurring post-discharge), explore protective factors (such as antimicrobial prophylaxis and its timing), and describe the epidemiology of SSI in terms of time of occurrence, microbiology, severity, patient outcome, and variation by procedure type, case-mix, and hospital size.

Aim 2: Determinants of SSI

In Aim 2, the investigators will study determinants of SSI in the following three areas:

  1. The surveillance system itself and how the thoroughness of the surveillance process correlates with reported SSI rates (Aim 2A)
  2. The operating room ventilation system and how its parameters correlate with SSI rates (Aim 2B)
  3. A healthcare institution’s perceived culture of safety and how it correlates with infection rates (Aim 2C)

To do so, the investigators will enhance and complement the Swissnoso SSI Surveillance data with new information at the institution level.

Aim 3: A mathematical model of surgical site infection

In Aim 3, the investigators will construct a mathematical model that simulates SSI pathogenesis based on data from Swissnoso and other sources, and assesses the impact of different preventive measures. Interventions will be ranked according to the simulated reduction of SSI rates in Switzerland.


Watussi-Teilstudie «Operating room ventilation and SSI rates»

Erhebung der lüftungstechnischen Merkmale von Operationssälen



Watussi-Teilstudie «Safety climate and SSI rates»

Befragung des OP-Personals im November 2019