Results
The total number of cases of SARS-CoV-2 infection amongst HCWs at CUHNFT
increased throughout the study period, in keeping with the rising
incidence of SARS-CoV-2 in the community (Figure 1 and Figure
1–source data 1 ). Similar proportions of cases were ascertained by
symptomatic testing and asymptomatic screening on both green and red
wards (Figure 1–figure supplement 1 ).
Prior to the change in RPE, cases per ward day were higher on red
compared with green wards in seven out of eight weeks analysed (p=0.016,
Wilcoxon signed-rank test, Figure 2 and Table 1 ).
Following the change in RPE, the incidence of infection on red and green
wards was similar, and not statistically different (p=0.5, Wilcoxon
signed-rank test, Figure 2 and Table 1 ). Strikingly,
there was a strong positive correlation between the incidence of
SARS-CoV-2 in the community and the number of cases per ward day on
green (R2=0.88) but not red wards
(R2 = 0.01) (Figure 2–figure supplement 1 ).
Taken together, these results suggest that the majority of cases among
HCWs on green wards were caused by community-acquired infection, whereas
cases among HCWs on red wards were caused by both community-acquired
infection and direct, ward-based infection from patients with COVID-19,
effectively mitigated by the use of FFP3 respirators.