Numerical modeling of nosocomial infection in a multi-bed ward environment

Abstract

A review on nosocomial infection has shown that there are various compelling evidence to suggest that the role of the airborne route to infection in a multi-bed environment cannot be ignored. Expiratory activities such as coughing, sneezes, talking and patient-centric activities such as bed-making has been shown in literature to generate significant quantity of infectious quanta that may become airborne and pose an infection threat to vulnerable patients. In this study, an airborne infection route of MRSA in the health care environment has been investigated using both the large-eddy simulation (LES) technique and an infection modeling. From analyzing flow field regimes in both a single room (typically found in isolation wards) and multi-bed ward environments, it was observed that the supply air delivered into the ventilated space produces pockets of recirculation areas near the walls and midway of the room in the wake of the advancing ventilation outlet bound flows, after impinging on internal surfaces such as beds. These recirculation areas have been identified as hot spots for possible airborne infection. Furthermore, the results suggests that the further the outlet vent is away from the inlet vent, the more likely will be the generation of recirculation regions, which directly translate to poor ventilation spots and that the use of curtains within the vicinity of the aerosol generating activities increases the number of recirculation areas. The overall airflow analysis suggest that any engineering solution designed to limit or remove the recirculation regions from the flow regime will be an effective way of fighting cross infections within the hospital ward environment, and as such ventilation schemes that are optimally designed to achieve this should be encouraged and investigated. This study has also predicted the possibility of a secondary infection in a multiward environment using various modeling approaches. The results obtained indicated that the posture of an infected person involved in the release of pathogens in relation to cohorts can have a profound effect on infection rates within the ward environment. The study of the coughing episode with the patient lying on the side generated a unit secondary infection, whilst the same simulated episode with an adjacent curtain in position failed to generate a secondary infection within the exposure period. The activity of bed making was also found to generate a secondary infection over the duration of the simulation, suggesting that bed-making can be a potential source of infection. The particle concentration decay curves examined in this work equally suggest that patients are at their most vulnerable state at the initial stages of coughing/sneezes, and talking episodes where the infecting patient assumes a directly facing posture to the susceptible