Concordance of SARS-CoV-2 RNA in Aerosols From a Nurses Station and in Nurses and Patients During a Hospital Ward Outbreak

Abstract

Importance: Aerosol-borne SARS-CoV-2 has not been linked specifically to nosocomial outbreaks.

Objective: To explore the genomic concordance of SARS-CoV-2 from aerosol particles of various sizes and infected nurses and patients during a nosocomial outbreak of COVID-19.

Design, setting, and participants: This cohort study included patients and nursing staff in a US Department of Veterans Affairs inpatient hospital unit and long-term-care facility during a COVID-19 outbreak between December 27, 2020, and January 8, 2021. Outbreak contact tracing was conducted using exposure histories and screening with reverse transcriptase-polymerase chain reaction (RT-PCR) for SARS-CoV-2. Size-selective particle samplers were deployed in diverse clinical areas of a multicampus health care system from November 2020 to March 2021. Viral genomic sequences from infected nurses and patients were sequenced and compared with ward nurses station aerosol samples.

Exposure: SARS-CoV-2.

Main outcomes and measures: The primary outcome was positive RT-PCR results and genomic similarity between SARS-CoV-2 RNA in aerosols and human samples. Air samplers were used to detect SARS-CoV-2 RNA in aerosols on hospital units where health care personnel were or were not under routine surveillance for SARS-CoV-2 infection.

Results: A total of 510 size-fractionated air particle samples were collected. Samples representing 3 size fractions (>10 μm, 2.5-10 μm, and <2.5 μm) obtained at the nurses station were positive for SARS-CoV-2 during the outbreak (3 of 30 samples [10%]) and negative during 9 other collection periods. SARS-CoV-2 partial genome sequences for the smallest particle fraction were 100% identical with all 3 human samples; the remaining size fractions shared >99.9% sequence identity with the human samples. Fragments of SARS-CoV-2 RNA were detected by RT-PCR in 24 of 300 samples (8.0%) in units where health care personnel were not under surveillance and 7 of 210 samples (3.3%; P = .03) where they were under surveillance.

Conclusions and relevance: In this cohort study, the finding of genetically identical SARS-CoV-2 RNA fragments in aerosols obtained from a nurses station and in human samples during a nosocomial outbreak suggests that aerosols may have contributed to hospital transmission. Surveillance, along with ventilation, masking, and distancing, may reduce the introduction of community-acquired SARS-CoV-2 into aerosols on hospital wards, thereby reducing the risk of hospital transmission.

Figure.. COVID-19 Outbreak Timeline and Ward A Layout

The timeline shows outbreak days 1 to 13, with nurse 1 (N1) presumed to be the outbreak source on the basis of earliest symptom onset. The patient room entrances were located 9 to 19 ft from the nurses station. Patient 1 (P1) wandered and spent time in front of the nurses station. The remaining patients occupied single- or double-occupancy rooms. ^aReverse transcriptase–polymerase chain reaction (PCR) cycle threshold (Ct) values shown; empty boxes indicate no available Ct value. ^bNo green box indicates that a patient or nurse was asymptomatic during the observation period. ^cCollector at the nurses station was sampling air between study days 10 and 13. ^dN10 and N11 were from a different ward; N10 tested positive on outbreak day 6 with a Ct of 15, and N11 tested positive on outbreak day 10 with a Ct of 17. N8 and N10 had a high-risk exposure to each other in the community before N10 tested positive.