Investigating SARS-CoV-2 surface and air contamination in an acute healthcare setting during the peak of the COVID-19 pandemic in London (preprint)

ABSTRACT

Objectives: To evaluate SARS-CoV-2 surface and air contamination during the peak of the COVID-19 pandemic in London. Design: Prospective cross-sectional observational study. Setting: An acute NHS healthcare provider. Participants: All inpatient wards were fully occupied by patients with COVID-19 at the time of sampling. Interventions: Air and surface samples were collected from a range of clinical areas and a public area of the hospital. An active air sampler was used to collect three or four 1.0 m3 air samples in each area. Surface samples were collected by swabbing approximately 25 cm2 of items in the immediate vicinity of each air sample. SARS-CoV-2 was detected by RT-qPCR and viral culture using Vero E6 and Caco2 cells; additionally the limit of detection for culturing SARS-CoV-2 dried onto surfaces was determined. Main outcome measures: SARS-CoV-2 detected by PCR or culture. Results: Viral RNA was detected on 114/218 (52.3%) of surface and 14/31 (38.7%) air samples but no virus was cultured. The proportion of surface samples contaminated with viral RNA varied by item sampled and by clinical area. Viral RNA was detected on surfaces and in air in public areas of the hospital but was more likely to be found in areas immediately occupied by COVID-19 patients (67/105 (63.8%) in areas immediately occupied by COVID-19 patients vs. 29/64 (45.3%) in other areas (odds ratio 0.5, 95% confidence interval 0.2-0.9, p=0.025, Fishers exact test). The PCR Ct value for all surface and air samples (>30) indicated a viral load that would not be culturable. Conclusions: Our findings of extensive viral RNA contamination of surfaces and air across a range of acute healthcare settings in the absence of cultured virus underlines the potential risk from surface and air contamination in managing COVID-19, and the need for effective use of PPE, social distancing, and hand/surface hygiene.