title: Modeling environmental contamination in hospital single- and four-bed rooms.
abstract: Aerial dispersion of pathogens is recognized as a potential transmission route for hospital acquired infections; however, little is known about the link between healthcare worker (HCW) contacts' with contaminated surfaces, the transmission of infections and hospital room design. We combine computational fluid dynamics (CFD) simulations of bioaerosol deposition with a validated probabilistic HCW-surface contact model to estimate the relative quantity of pathogens accrued on hands during six types of care procedures in two room types. Results demonstrate that care type is most influential (P < 0.001), followed by the number of surface contacts (P < 0.001) and the distribution of surface pathogens (P = 0.05). Highest hand contamination was predicted during Personal care despite the highest levels of hand hygiene. Ventilation rates of 6 ac/h vs. 4 ac/h showed only minor reductions in predicted hand colonization. Pathogens accrued on hands decreased monotonically after patient care in single rooms due to the physical barrier of bioaerosol transmission between rooms and subsequent hand sanitation. Conversely, contamination was predicted to increase during contact with patients in four-bed rooms due to spatial spread of pathogens. Location of the infectious patient with respect to ventilation played a key role in determining pathogen loadings (P = 0.05).
  
  
  CONCLUSIONS
  We present the first quantitative model predicting the surface contacts by HCW and the subsequent accretion of pathogenic material as they perform standard patient care. This model indicates that single rooms may significantly reduce the risk of cross-contamination due to indirect infection transmission. Not all care types pose the same risks to patients, and housekeeping performed by HCWs may be an important contribution in the transmission of pathogens between patients. Ventilation rates and positioning of infectious patients within four-bed rooms can mitigate the accretion of pathogens, whereby reducing the risk of missed hand hygiene opportunities. The model provides a tool to quantitatively evaluate the influence of hospital room design on infection risk.
authors.affiliation: School of Civil Engineering, Pathogen Control Engineering Institute, University of Leeds, Leeds, UK.
authors.forename: M-F
authors.initials: MF
authors.lastname: King
authors.affiliation: School of Civil Engineering, Pathogen Control Engineering Institute, University of Leeds, Leeds, UK.
authors.forename: C J
authors.initials: CJ
authors.lastname: Noakes
authors.affiliation: School of Civil Engineering, Pathogen Control Engineering Institute, University of Leeds, Leeds, UK.
authors.forename: P A
authors.initials: PA
authors.lastname: Sleigh
mesh_terms: D003428:Cross Infection / Q000517:prevention & control / Q000635:transmission*; D006235:Hand Disinfection; D006801:Humans; D057446:Hydrodynamics; D017757:Infectious Disease Transmission, Professional-to-Patient; D008954:Models, Biological; D005791:Patient Care; D010362:Patients' Rooms; D014691:Ventilation
keywords: Bioaerosol; CFD; HCAI; Hand contamination; Indirect transmission; Markov chain