Modelling the Risk of Infection Transmission due to Environmental Contamination in Hospital Single and Multi-bed Rooms

INTRODUCTION: Risk of acquiring hospital acquired infections is omnipresent in health-care facilities worldwide and understanding transmission routes is key to effective control. Aerial dispersion of bioaerosols and subsequent contamination of surfaces is recognised as a potential transmission route for some of these infections. Pathogens have been shown to accrue on health-care workers’ (HCW) hands as they touch surfaces and hence can subsequently be transmitted to other patients. This research considers the question: Are single-bed patient rooms more effective than their multi-bed counterparts at reducing this risk?

METHODS: Computational fluid dynamics (CFD) simulations, validated through bioaerosol experiments (King et al 2013) were used to accurately predict spatial distributions of bioaerosol deposition in a single and multi-bed hospital rooms. A Markov chain Monte-Carlo model was developed using the deposition patterns in conjunction with clinical observation of HCW surface contact sequences, to predict the contamination levels of bacteria on HCWs’ hands as they perform routine patient care in the two rooms types.

RESULTS: Results demonstrate that hand colonisation depends on care type, room layout, the number of surface contacts and in particular on the spatial distribution of pathogens between surfaces, which is influenced by ventilation strategy. Contamination on the HCWs' hands decreases monotonically after patient care in a single room due to hand hygiene. During care within multi-bed rooms colonisation levels increase throughout due to the spatial spread of microorganisms contaminating multiple patient surfaces caused by the ventilation strategy. Positioning infectious patients within an unobstructed path between the inlet and outlet diffuser significantly reduces cross contamination to other patients surfaces.

CONCLUSIONS: Results indicate that colonisation levels of HCWs’ hands are likely to be significantly lower after care in single patient rooms than after care in a multi-bed ward and that patient and ventilation design is vitally important in helping curtail the risk of bioaerosol spread.