gms | German Medical Science

51. Jahrestagung der Deutschen Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie

Deutsche Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie e. V. (gmds)

10. - 14.09.2006, Leipzig

Modelling the transmission dynamics of nosocomial pathogens with data of a recent VRE-outbreak at a University Hospital

Meeting Abstract

  • Martin Wolkewitz - Universitätsklinikum Freiburg, Freiburg
  • Markus Dettenkofer - Universitätsklinikum Freiburg, Freiburg
  • Johannes Huebner - Universitätsklinikum Freiburg, Freiburg
  • Martin Schumacher - Universitätsklinikum Freiburg, Freiburg

Deutsche Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie e.V. (gmds). 51. Jahrestagung der Deutschen Gesellschaft für Medizinische Informatik, Biometrie und Epidemiologie. Leipzig, 10.-14.09.2006. Düsseldorf, Köln: German Medical Science; 2006. Doc06gmds097

The electronic version of this article is the complete one and can be found online at:

Published: September 1, 2006

© 2006 Wolkewitz et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.




Nosocomial infections due to multi-resistent pathogens like vancomycin-resistent enterococci (VRE) or methicillin-resistant staphylococcus aureus (MRSA) are a major infection control problem, especially in intensive-care and haematology units. Beside increasing costs, they play an important role in prolonging the length of stay in hospitals. Several outbreaks of VRE have occurred in hospitals in the United States and in Europe, especially in older patients and patients with a compromised immune system. Intervention strategies are essential to control the outbreak and reduce transmisson of multi-resistent pathogens. Mathematical modelling can help to understand the transmission dynamics and the pattern of spread, especially when exploring the impact of interventions.


Austin et al. [1], [2] applied the deterministic Ross-Macdonald model [3] which originally models vector-borne malaria transmission. This model will be used for the VRE transmission via hands of health-care workers. Differential equations describe the temporal transmission dynamics of an VRE-outbreak on a unit or a department under specific conditions. We collected data from an outbreak of VRE between June 2004 and August 2005 at the University Hospital of Freiburg, where more than 100 patients were colonised or infected with VRE [4]. Several important parameters like the basis reproduction number, admission colonisation prevalence, length of stay etc. could be identified. These were included in the model; Gaussian noise was superimposed to get information about precision. Additional to the deterministic models, stochastic simulations via counting processes were performed.


Descriptive results of the outbreak at Freiburg University Hospital will be presented. With these models, we are able to determine the final size of this outbreak and predict the effect of intervention strategies like hand hygiene, cohorting infected patients and reduction of antibiotics usage in order to get an infection-free steady state. Graphical results show which combinations of these strategies are appropriate for varying values and different scenarios. Thus, these results can be applied to other settings and will therefore help to understand and control epidemic spread of nosocomial pathogens.


In the deterministic Ross-Macdonald model only the indirect transmission via hands of health-care workers is modelled, but there might be additional ways for the pathogen to infect humans. A VRE-transmission might also be possible if patients share the same washrooms or toilets. An extension of the Ross-Macdonald model, where this kind of transmission will be taken into account, will be discussed.


Austin et al. Vancomycin-resistant enterococci in intensive-care hospital settings: transmission dynamics, persistence, and the impact of infection control programs. Proc Natl Acad Sci USA 1999; 96:6908-13.
Grundmann et al. Risk Factors for the Transmission of Methicillin-Resistant Staphylococcus aureus in an Adult Intensive Care Unit: Fitting a Model to the Data. The Journal of Infectious Diseases 2002;185:481-488
Anderson and May (1991) Infectious Diseases of Humans: Dynamics and Control (Oxford Univ. Press Oxford)
Mlangeni D et al. Management of an outbreak of vancomycin-resistent enterococci (VRE) in a German university hospital hemato-oncology department. Poster, ECCMID 2006, Nice