SARS-CoV-2 indoor environment contamination with epidemiological and experimental investigations

Abstract

SARS-CoV-2 has been detected both in air and on surfaces, but questions remain about the patient-specific and environmental factors affecting virus transmission. Additionally, more detailed information on viral sampling of the air is needed. This prospective cohort study (N = 56) presents results from 258 air and 252 surface samples from the surroundings of 23 hospitalized and eight home-treated COVID-19 index patients between July 2020 and March 2021 and compares the results between the measured environments and patient factors. Additionally, epidemiological and experimental investigations were performed. The proportions of qRT-PCR-positive air (10.7% hospital/17.6% homes) and surface samples (8.8%/12.9%) showed statistical similarity in hospital and homes. Significant SARS-CoV-2 air contamination was observed in a large (655.25 m³ ) mechanically ventilated (1.67 air changes per hour, 32.4-421 L/s/patient) patient hall even with only two patients present. All positive air samples were obtained in the absence of aerosol-generating procedures. In four cases, positive environmental samples were detected after the patients had developed a neutralizing IgG response. SARS-CoV-2 RNA was detected in the following particle sizes: 0.65-4.7 μm, 7.0-12.0 μm, >10 μm, and <100 μm. Appropriate infection control against airborne and surface transmission routes is needed in both environments, even after antibody production has begun.

Keywords: SARS-CoV-2; air sample; infection control; neutralizing antibody response; surface sample.

FIGURE 1

Patient inclusion and sampling process and additional analysis performed in the study

FIGURE 2

Sampling set up. (A) Layout of the COVID‐19 cohort ward. (B) Layout of the single‐patient room. (C) Locations of the sampling spots for the active air samplers around the patient (1: Andersen, 2: BioSpot, 3: Button, 4: Dekati, and 5: eFilter). (D) Example locations of the surface sampling spots and deposition sample spots around the patient, a: window sill, b: computer, c: bed rail, d: bed remote, e: table, f: drinking glass, g: floor, h: hospital equipment. (E) Location of the surface sampling spots in the toilet, i: door handle, j: toilet bowl, k: tap, l: toilet seat, m: toilet flush button. The figure was created with Adobe Illustrator 2020 (24.0.2)