SARS-CoV-2 environmental contamination associated with persistently infected COVID-19 patients

Abstract

Background: Severe COVID-19 patients typically test positive for SARS-CoV-2 RNA for extended periods of time, even after recovery from severe disease. Due to the timeframe involved, these patients may have developed humoral immunity to SARS-CoV-2 while still testing positive for viral RNA in swabs. Data are lacking on exposure risks in these situations. Here, we studied SARS-CoV-2 environmental contamination in an ICU and an isolation ward caring for such COVID-19 patients.

Methods: We collected air and surface samples in a hospital caring for critical and severe COVID-19 cases from common areas and areas proximal to patients.

Results: Of the 218 ICU samples, an air sample contained SARS-CoV-2 RNA. Of the 182 isolation ward samples, nine contained SARS-CoV-2 RNA. These were collected from a facemask, the floor, mobile phones, and the air in the patient room and bathroom. Serum antibodies against SARS-CoV-2 were detected in these patients at the beginning of the study.

Conclusions: While there is a perception of increased risk in the ICU, our study demonstrates that isolation wards may pose greater risks to healthcare workers and exposure risks remain with clinically improved patients, weeks after their initial diagnoses. As these patients had serum antibodies, further studies may be warranted to study the utility of serum antibodies as a surrogate of viral clearance in allowing people to return to work. We recommend continued vigilance even with patients who appear to have recovered from COVID-19.

Keywords: COVID-19; SARS-CoV-2; coronavirus; intensive care unit; transmission.

Figure 1

Arrangement of the NIOSH cyclonic bioaerosol sampler. A, Arrangement of the NIOSH sampler on a tripod next to the head of the patient's bed with the temperature, humidity, and carbon dioxide monitor used in this study. B, NIOSH sampler showing collection tubes and collection filter and the particle sizes collected in each

Figure 2

Summary of viral loads in patient swabs, clinical care procedures performed during sampling, and outcomes of environmental sampling. Timeline shows samples collected from patients and testing results for SARS‐CoV‐2 RNA by quantitative real‐time PCR in the (A) intensive care unit and (B) in the isolation ward. Environmental samples that tested positive for SARS‐CoV‐2 RNA by quantitative real‐time PCR are also shown

Figure 3

Layouts of hospital rooms. Samples were collected in the intensive care unit (ICU) (A) and in an isolation ward (B). In the ICU, airflow originated in the ceiling above the foot of each patient bed and was extracted through vents in the wall at bed height. Placement of the NIOSH and DingBlue air samplers and bed numbers are shown. The red triangle indicates the handwashing station that was sampled. In the isolation ward, each patient was isolated in different rooms with their own bathrooms. The locations of the NIOSH and DingBlue air samplers are shown in their positions relative to the patient's bed, toilet, and bathroom sink. Diagrams are not to scale. Refer to Table 1 for a list of air and environmental samples collected