An integrated model of infection risk in a health-care environment

Risk Anal. 2006 Aug;26(4):1085-96. doi: 10.1111/j.1539-6924.2006.00802.x.


Certain respiratory tract infections can be transmitted by hand-to-mucous-membrane contact, inhalation, and/or direct respiratory droplet spray. In a room occupied by a patient with such a transmissible infection, pathogens present on textile and nontextile surfaces, and pathogens present in the air, provide sources of exposure for an attending health-care worker (HCW); in addition, close contact with the patient when the latter coughs allows for droplet spray exposure. We present an integrated model of pertinent source-environment-receptor pathways, and represent physical elements in these pathways as "states" in a discrete-time Markov chain model. We estimate the rates of transfer at various steps in the pathways, and their relationship to the probability that a pathogen in one state has moved to another state by the end of a specified time interval. Given initial pathogen loads on textile and nontextile surfaces and in room air, we use the model to estimate the expected pathogen dose to a HCW's mucous membranes and respiratory tract. In turn, using a nonthreshold infectious dose model, we relate the expected dose to infection risk. The system is illustrated with a hypothetical but plausible scenario involving a viral pathogen emitted via coughing. We also use the model to show that a biocidal finish on textile surfaces has the potential to substantially reduce infection risk via the hand-to-mucous-membrane exposure pathway.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Cough / microbiology
  • Hand / microbiology
  • Humans
  • Infection Control
  • Infections / transmission*
  • Infectious Disease Transmission, Patient-to-Professional*
  • Markov Chains
  • Models, Biological*
  • Mucous Membrane / microbiology
  • Respiratory System / microbiology
  • Respiratory Tract Infections / prevention & control
  • Respiratory Tract Infections / transmission
  • Risk Assessment
  • Textiles