Modelling the joint effects of single occupancy and N95 respirators on COVID-19 outbreaks in hospital wards.

BACKGROUND

Outbreaks of respiratory pathogens on hospital wards present challenges for control of hospital-acquired infections.

AIM: To investigate the potential for synergistic effects between structural controls (single-occupancy patient rooms) and routine precautions (use of N95 respirators by healthcare staff), in preventing and mitigating outbreaks of airborne pathogens on hospital wards.

METHODS

This study applied an agent-based extension of the Wells-Riley model of airborne pathogen exposure to simulate COVID-19 outbreaks on hospital wards. Secondary attack rates and the sizes of outbreaks resulting from introduction of unrecognized cases in hospital wards with double- or single-occupancy patient rooms were simulated. The impact of N95 respirator use by nurses during patient care activities was simulated, assuming an efficacy of 90% for protection and source control.

FINDINGS: The size of simulated outbreaks recorded at day 14 was markedly lower in wards with only single-occupancy rooms, compared to double-occupancy rooms (with means of 14.1 and 22.8 infections, respectively). Nurses were more likely to acquire infection than patients for both single- and double-occupancy scenarios. Single occupancy was associated with smaller outbreak sizes, with a larger relative impact on patients than on staff. N95 respirators were effective at mitigating outbreaks, with higher impacts in wards with single-occupancy patient rooms.

CONCLUSION

Our results are consistent with claims that single-occupancy patient rooms reduce transmission of SARS-CoV-2 on hospital wards. Our findings also support the claim that use of N95 respirators by nurses when caring for patients can reduce the effective reproductive ratio of the pathogen. Finally, we demonstrated that switching to single occupancy can increase the benefit of N95 respirator use by healthcare staff.