key: cord-0995667-39hgfbi0
authors: Izzotti, A.; Grasselli, E.; Barbaresi, M.; Bixio, M.; Colombo, M.; Pfeffer, U.; Pulliero, A.; Sossai, D.; Borneto, A.; Boccaccio, A.; Manfredi, V.; Bassetti, M.; Nicosia, E.; Tiso, M.
title: Development of an integrated environmental monitoring protocol for SARS-CoV-2 contamination. Applications at the IRCSS San Martino Polyclinic Hospital in Genoa, Italy
date: 2022-01-29
journal: Environ Res
DOI: 10.1016/j.envres.2022.112790
sha: 52e7e3418a74e866b54ac6353b6f0a9e7b3a7b69
doc_id: 995667
cord_uid: 39hgfbi0

SCIENTIFIC BACKGROUND: Environmental sampling of SARS-CoV-2 is a fundamental tool for evaluating the effectiveness of non-specific prophylaxis measures in counting their 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 was carried out at the San Martino Polyclinic Hospital (Genoa, Italy) in the period from April 2020 to June 2021. The presence of viral RNA in the collected samples was evaluated by qPCR. The infection capacity of the sample 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 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 patient. 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 is not a degraded viral fragment but an intact infecting virion, only in a modest percentage of cases.

SARS-CoV-2 is mainly transmitted through infected respiratory droplets and close contact with the 66 infected person. (Riou and Althaus 2020). Furthermore, there is a risk for aerosol transmission 67 when the virus is exposed to high concentrations of aerosol for a long time in a relatively closed 68 environment. SARS-CoV-2 virus is highly contagious, and people are severely susceptible to it. 69 Many healthcare workers have been infected during patient care during this pandemic. (Wang ,et 70 al., 2020) . Environmental sampling of SARS-CoV-2 is considered as a fundamental tool for the 71 prevention of the COVID-19 infection. For this reason, the sampling that allows to define the 72 spreading characteristics of the virus and guides the measures of non-specific environmental 73 prophylaxis, is aimed at offsetting its spread. In addition, environmental sampling makes it possible 74 to identify the effectiveness of the prophylaxis and disinfection measures implemented to hold 75 SARS-CoV-2 contagion in confined environments (van Doremalen 2020). WHO defines droplets 76 and droplet nuclei of more than 5 μm in diameter as respiratory aerosols and the residue of up to 77 5 μm in diameter as dried respiratory aerosols, produced by the evaporation of droplets coughed or 78 sneezed into the atmosphere or aerosolized infective material, respectively (WHO 2014) . Liu et al. 79 reported that the peak concentration of SARS-CoV-2 aerosols appears in two distinct size ranges: at 80 the submicron scale with dominant aerodynamic diameter between 0.25 and 1.0 μm; and at the 81 supermicron scale with diameter greater than 2.5 μm (Liu Y, 2020) . The main sources of CoV-2 aerosols are coughs and sneezes by infected people. The capacity for droplets to travel long 83 distances in airflow is determined largely by their size. (Kampf 2020) . 84 The environmental sampling can be carried out in the following ways: (a) wipe test; (b) sampling of 85 the airborne viral suspension. (Becker et al., 2019) . The wipe test allows a cumulative assessment of 86 the viral load that is deposited over time with reference especially to that carried by the large 87 aerosol (droplet); it is not quantitative sampling. The sampling of the air diffuse suspension allows 88 the quantitative evaluation of the viral load per cubic meter of sampled air; reflects the viral load 89 also present in the small aerosol which by its nature tends to settle much more slowly over time than 90 in the large aerosol. For this reason, the small aerosol spreads at a much greater distance than the The purpose of our work was to evaluate the effectiveness of environmental sampling for SARS-

CoV-2 in the hospital setting to compare and integrate the information provided by different 106 sampling methods. The results obtained were used to evaluate the correlation between 107 environmental sampling and the structural, functional, and operational situation of the monitored 108 departments.

The specific aim of our work was to develop a complementary environmental sampling method for 

A total 29 swab samples were collected within the twelve sampling sites at the Emergency CoV-2 in the DEA Department by bubbler were positive for PCR test to 37.5 in Air near (50 cm) to 219 the patients at bed of 80 cm height. (Tab. 5). The positive rate was 20% with wipe test, and 43% 220 with bubbler sampling. The higher positivity rate was measured by challenge test, near air (<1m) 221 from patients at 0.6m height as compared to the bubbler sampling (Tab 6).

The wipe test showed a sensitivity of 17%, and 83% negatives for viral RNA (Tab 8). The in Tab 8. The positivity rate observed by wipe test was 17% for <1 m from patient, and was 50% by 227 <2m height and by <1 m from patient, detected by bubbler sampling, the positivity rate was 11% 228 measured by challenge test <1 m and height 80 cm and 0.6 m from patient (Tab 8).

The challenge test was the only one used to directly assess the ability of the virus to penetrate (Otter J.A. et al., 2016) . Also, 299 infecting virions have not been detected above 1.5 m in height and specifically in the vicinity of the 300 air intake vents of the aeraulic systems. It therefore appears extremely unlikely that SARS-CoV-2 301 will spread through such implants unless the suction port is located less than 1.5m high and less 302 than 2m from the patient. Therefore, it does not seem appropriate to carry out excessive sanitization 303 procedures of these plants and their closure, which would decrease the air circulation thus 304 decreasing the per capita air cube and increasing the environmental viral load. Furthermore, the 305 decrease in ventilation and air cooling with the consequent loss of optimization of the indoor 306 environmental temperature could have negative influences on mortality especially during the 307 summer and increasingly frequent heat wave months (Zhao et al., 2021) . Available data indicates 308 that SARS-CoV-2 spreads more rapidly than Severe acute respiratory syndrome (SARS) and Cov-2 using a membrane sampler similar to the one we used on 52 samples and by wipe test on 320 331 samples (Kim et al., 2020) . All the samples collected by membrane sampler were negative, like 332 what we found at the San Martino Polyclinic using the same sampler. 27% of the wipe tests were 333 positive, a value higher than the 17% we observed at the San Martino Polyclinic where only wards 334 with a high risk of contamination were examined. It is interesting to note that this study also 335 identifies the distance from patients as a factor strongly influencing the positivity of the samples. In 

The presence of SARS-CoV-2 in the environment was investigated in the hospital of the National 345 Center for Infectious Diseases in Singapore (China) (Chia et al., 2020) . The presence of the virus as 346 an air-diffused feed was evaluated with an aerosol sampler by collecting the particulate matter of 347 dimensions between 1 and 4 microns. The sampling of the surfaces was carried out by wipe test. Genoa. It is interesting to note that the positivity observed in this study was all related to the larger 351 particle sizes while the virus was not detectable in the particle sizes with dimensions less than 1 um 352 and the viral load was proportional to the size of the particle size. This result confirms that SARS- Table 9 . Number of positive samples whose positivity is also confirmed by the challenge test. Table 9 . Number of positive samples whose positivity is also confirmed by the challenge test. 

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Writing-Original draft preparation

Izzotti A. Nicosia E, Tiso M 6 Investigation. Izzotti A. and Tiso M Supervision. Izzotti A., Grasselli E., and Tiso M Validation

Writing-Reviewing and Editing

This study was supported by Regione Liguria Project 'Evaluation of infectiveness of pathogen 411 viruses in water' (DR 2020 -AC-182, 26/5/2020 ) and by Gadomed S.r.l. Genoa, Italy.

A thank goes to Zumama Khalid, a PhD student for her help with the English language revision. x 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.☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:J o u r n a l P r e -p r o o f