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. 2022 Jun:209:112790.
doi: 10.1016/j.envres.2022.112790. Epub 2022 Jan 29.

Development of an integrated environmental monitoring protocol for SARS-CoV-2 contamination. Applications at the IRCSS San Martino Polyclinic Hospital in Genoa, Italy

A Izzotti  1 , E Grasselli  2 , M Barbaresi  3 , M Bixio  4 , M Colombo  5 , U Pfeffer  6 , A Pulliero  7 , D Sossai  8 , A Borneto  9 , A Boccaccio  10 , V Manfredi  11 , M Bassetti  12 , E Nicosia  13 , M Tiso  14
Affiliations

Development of an integrated environmental monitoring protocol for SARS-CoV-2 contamination. Applications at the IRCSS San Martino Polyclinic Hospital in Genoa, Italy

A Izzotti et al. Environ Res. 2022 Jun.

Abstract

Scientific background: Environmental sampling of SARS-CoV-2 is a fundamental tool for evaluating the effectiveness of non-specific prophylaxis measures in counteracting virus spread. The purpose of our work was to evaluate the effectiveness of the different sampling methods in the hospital setting to assess their correlation with the structural, functional, and operational situation of the monitored departments and to define the dynamics of the spread of the virus in indoor environments.

Methods: The monitoring (air bubbling sampling, surface wipe test) was carried out at the San Martino Polyclinic Hospital (Genoa, Italy) in the period since April 2020 to June 2021. The presence of viral RNA in the collected samples was evaluated by qPCR. The infection capacity of the samples collected was also evaluated by an in vitro challenge test on cells sensitive to SARS-CoV-2 infection.

Results: The percentage of positivity with respect to the number of tests performed (sensitivity) were air bubbler 50%, wipe test 17%, and challenge test 11%. Only 20% of the samples tested positive in the wipe test and 43% of the samples tested positive in the bubbler sampling were also positive in the challenge test. All the positivity obtained was detected at a distance of less than 2 m and height of less than 1.5 from COVID-19 patients.

Conclusions: Environmental contamination from SARS-CoV-2 detected at the San Martino Polyclinic Hospital is found lower than similar assessments performed in other hospitals both in Italy and abroad. Our study predicted that environmental monitoring of SARS-CoV-2 must be carried out in an integrated way by not using a single sampling method, as each individual test has a different biological significance and performance. However, the virus detected by wipe test only is often a degraded viral fragment and not an intact infecting virion.

Keywords: Challenge test; Environmental monitoring; Hospital contamination; SARS-CoV-2; Viral RNA.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Environmental sampling methods: wipe test, membrane sampling and bubbling air sampler.
Fig. 2
Fig. 2
Schematic diagram showing environmental sampling sites in the inpatient area of the hospital. The presence of the virus is indicated in red and the absence in green. Contaminated areas are those close air (<1 m) at patients at 1.5 m of height for 1 h. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
See this image and copyright information in PMC

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