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      Affordable measures to monitor and alarm nosocomial SARS‐CoV‐2 infection due to poor ventilation

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          Abstract

          Since the coronavirus disease 2019 (COVID‐19) outbreak, the nosocomial infection rate worldwide has been reported high. It is urgent to figure out an affordable way to monitor and alarm nosocomial infection. Carbon dioxide (CO 2) concentration can reflect the ventilation performance and crowdedness, so CO 2 sensors were placed in Beijing Tsinghua Changgung Hospital's fever clinic and emergency department where the nosocomial infection risk was high. Patients’ medical records were extracted to figure out their timelines and whereabouts. Based on these, site‐specific CO 2 concentration thresholds were calculated by the dilution equation and sites’ risk ratios were determined to evaluate ventilation performance. CO 2 concentration successfully revealed that the expiratory tracer was poorly diluted in the mechanically ventilated inner spaces, compared to naturally ventilated outer spaces, among all of the monitoring sites that COVID‐19 patients visited. Sufficient ventilation, personal protection, and disinfection measures led to no nosocomial infection in this hospital. The actual outdoor airflow rate per person ( Q c) during the COVID‐19 patients’ presence was estimated for reference using equilibrium analysis. During the stay of single COVID‐19 patient wearing a mask, the minimum Q c value was 15–18 L/(s·person). When the patient was given throat swab sampling, the minimum Q c value was 21 L/(s·person). The Q c value reached 36–42 L/(s·person) thanks to window‐inducted natural ventilation, when two COVID‐19 patients wearing masks shared the same space with other patients or healthcare workers. The CO 2 concentration monitoring system proved to be effective in assessing nosocomial infection risk by reflecting real‐time dilution of patients’ exhalation.

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          Clinical Characteristics of 138 Hospitalized Patients With 2019 Novel Coronavirus–Infected Pneumonia in Wuhan, China

          Dawei Wang, Bo Hu, Fangfang Zhu … (2020)
          In December 2019, novel coronavirus (2019-nCoV)-infected pneumonia (NCIP) occurred in Wuhan, China. The number of cases has increased rapidly but information on the clinical characteristics of affected patients is limited.
          Article 0 comments Cited 10911 times – based on 0 reviews     Review now
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            Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1

            Neeltje van Doremalen, Trenton Bushmaker, Dylan H Morris … (2021)
            To the Editor: A novel human coronavirus that is now named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (formerly called HCoV-19) emerged in Wuhan, China, in late 2019 and is now causing a pandemic. 1 We analyzed the aerosol and surface stability of SARS-CoV-2 and compared it with SARS-CoV-1, the most closely related human coronavirus. 2 We evaluated the stability of SARS-CoV-2 and SARS-CoV-1 in aerosols and on various surfaces and estimated their decay rates using a Bayesian regression model (see the Methods section in the Supplementary Appendix, available with the full text of this letter at NEJM.org). SARS-CoV-2 nCoV-WA1-2020 (MN985325.1) and SARS-CoV-1 Tor2 (AY274119.3) were the strains used. Aerosols (<5 μm) containing SARS-CoV-2 (105.25 50% tissue-culture infectious dose [TCID50] per milliliter) or SARS-CoV-1 (106.75-7.00 TCID50 per milliliter) were generated with the use of a three-jet Collison nebulizer and fed into a Goldberg drum to create an aerosolized environment. The inoculum resulted in cycle-threshold values between 20 and 22, similar to those observed in samples obtained from the upper and lower respiratory tract in humans. Our data consisted of 10 experimental conditions involving two viruses (SARS-CoV-2 and SARS-CoV-1) in five environmental conditions (aerosols, plastic, stainless steel, copper, and cardboard). All experimental measurements are reported as means across three replicates. SARS-CoV-2 remained viable in aerosols throughout the duration of our experiment (3 hours), with a reduction in infectious titer from 103.5 to 102.7 TCID50 per liter of air. This reduction was similar to that observed with SARS-CoV-1, from 104.3 to 103.5 TCID50 per milliliter (Figure 1A). SARS-CoV-2 was more stable on plastic and stainless steel than on copper and cardboard, and viable virus was detected up to 72 hours after application to these surfaces (Figure 1A), although the virus titer was greatly reduced (from 103.7 to 100.6 TCID50 per milliliter of medium after 72 hours on plastic and from 103.7 to 100.6 TCID50 per milliliter after 48 hours on stainless steel). The stability kinetics of SARS-CoV-1 were similar (from 103.4 to 100.7 TCID50 per milliliter after 72 hours on plastic and from 103.6 to 100.6 TCID50 per milliliter after 48 hours on stainless steel). On copper, no viable SARS-CoV-2 was measured after 4 hours and no viable SARS-CoV-1 was measured after 8 hours. On cardboard, no viable SARS-CoV-2 was measured after 24 hours and no viable SARS-CoV-1 was measured after 8 hours (Figure 1A). Both viruses had an exponential decay in virus titer across all experimental conditions, as indicated by a linear decrease in the log10TCID50 per liter of air or milliliter of medium over time (Figure 1B). The half-lives of SARS-CoV-2 and SARS-CoV-1 were similar in aerosols, with median estimates of approximately 1.1 to 1.2 hours and 95% credible intervals of 0.64 to 2.64 for SARS-CoV-2 and 0.78 to 2.43 for SARS-CoV-1 (Figure 1C, and Table S1 in the Supplementary Appendix). The half-lives of the two viruses were also similar on copper. On cardboard, the half-life of SARS-CoV-2 was longer than that of SARS-CoV-1. The longest viability of both viruses was on stainless steel and plastic; the estimated median half-life of SARS-CoV-2 was approximately 5.6 hours on stainless steel and 6.8 hours on plastic (Figure 1C). Estimated differences in the half-lives of the two viruses were small except for those on cardboard (Figure 1C). Individual replicate data were noticeably “noisier” (i.e., there was more variation in the experiment, resulting in a larger standard error) for cardboard than for other surfaces (Fig. S1 through S5), so we advise caution in interpreting this result. We found that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1 under the experimental circumstances tested. This indicates that differences in the epidemiologic characteristics of these viruses probably arise from other factors, including high viral loads in the upper respiratory tract and the potential for persons infected with SARS-CoV-2 to shed and transmit the virus while asymptomatic. 3,4 Our results indicate that aerosol and fomite transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days (depending on the inoculum shed). These findings echo those with SARS-CoV-1, in which these forms of transmission were associated with nosocomial spread and super-spreading events, 5 and they provide information for pandemic mitigation efforts.
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              Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis

              Derek K. Chu, Elie A. Akl, Stephanie Duda … (2020)
              Summary Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 and is spread person-to-person through close contact. We aimed to investigate the effects of physical distance, face masks, and eye protection on virus transmission in health-care and non-health-care (eg, community) settings. Methods We did a systematic review and meta-analysis to investigate the optimum distance for avoiding person-to-person virus transmission and to assess the use of face masks and eye protection to prevent transmission of viruses. We obtained data for SARS-CoV-2 and the betacoronaviruses that cause severe acute respiratory syndrome, and Middle East respiratory syndrome from 21 standard WHO-specific and COVID-19-specific sources. We searched these data sources from database inception to May 3, 2020, with no restriction by language, for comparative studies and for contextual factors of acceptability, feasibility, resource use, and equity. We screened records, extracted data, and assessed risk of bias in duplicate. We did frequentist and Bayesian meta-analyses and random-effects meta-regressions. We rated the certainty of evidence according to Cochrane methods and the GRADE approach. This study is registered with PROSPERO, CRD42020177047. Findings Our search identified 172 observational studies across 16 countries and six continents, with no randomised controlled trials and 44 relevant comparative studies in health-care and non-health-care settings (n=25 697 patients). Transmission of viruses was lower with physical distancing of 1 m or more, compared with a distance of less than 1 m (n=10 736, pooled adjusted odds ratio [aOR] 0·18, 95% CI 0·09 to 0·38; risk difference [RD] −10·2%, 95% CI −11·5 to −7·5; moderate certainty); protection was increased as distance was lengthened (change in relative risk [RR] 2·02 per m; p interaction=0·041; moderate certainty). Face mask use could result in a large reduction in risk of infection (n=2647; aOR 0·15, 95% CI 0·07 to 0·34, RD −14·3%, −15·9 to −10·7; low certainty), with stronger associations with N95 or similar respirators compared with disposable surgical masks or similar (eg, reusable 12–16-layer cotton masks; p interaction=0·090; posterior probability >95%, low certainty). Eye protection also was associated with less infection (n=3713; aOR 0·22, 95% CI 0·12 to 0·39, RD −10·6%, 95% CI −12·5 to −7·7; low certainty). Unadjusted studies and subgroup and sensitivity analyses showed similar findings. Interpretation The findings of this systematic review and meta-analysis support physical distancing of 1 m or more and provide quantitative estimates for models and contact tracing to inform policy. Optimum use of face masks, respirators, and eye protection in public and health-care settings should be informed by these findings and contextual factors. Robust randomised trials are needed to better inform the evidence for these interventions, but this systematic appraisal of currently best available evidence might inform interim guidance. Funding World Health Organization.
              Article 0 comments Cited 1770 times – based on 0 reviews     Review now
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                Author and article information

                Contributors
                Borong Lin: linbr@tsinghua.edu.cn
                Minggui Lin: linminggui309301@126.com
                Li Liu:
                ORCID: https://orcid.org/0000-0001-8512-8676
                liuli_archi@tsinghua.edu.cn
                Journal
                Journal ID (nlm-ta): Indoor Air
                Journal ID (iso-abbrev): Indoor Air
                Journal ID (doi): 10.1111/(ISSN)1600-0668
                Journal ID (publisher-id): INA
                Title: Indoor Air
                Publisher: John Wiley and Sons Inc. (Hoboken )
                ISSN (Print): 0905-6947
                ISSN (Electronic): 1600-0668
                Publication date (Electronic): 28 June 2021
                Publication date PMC-release: 28 June 2021
                Electronic Location Identifier: 10.1111/ina.12899
                Affiliations
                [ 1 ] Department of Building Science Tsinghua University Beijing China
                [ 2 ] Key Laboratory of Eco‐Planning & Green Building Ministry of Education Tsinghua University Beijing China
                [ 3 ] Department of Disease & Nosocomial infection control Beijing Tsinghua Changgung Hospital Beijing China
                [ 4 ] School of Clinical Medicine Tsinghua University Beijing China
                [ 5 ] Department of radiology Beijing Tsinghua Changgung Hospital Beijing China
                [ 6 ] Peking‐Tsinghua Center for Life Sciences Tsinghua University Beijing China
                [ 7 ] Department of Infection Beijing Tsinghua Changgung Hospital Beijing China
                Author notes
                [*] [* ] Correspondence

                Li Liu and Borong Lin Department of Building Science, Tsinghua University, Beijing 100084, China.

                Minggui Lin, Department of Infection, Beijing Tsinghua Changgung Hospital, Beijing 102218, China.

                Emails: liuli_archi@ 123456tsinghua.edu.cn (L L); linbr@ 123456tsinghua.edu.cn (B L); linminggui309301@ 123456126.com (M L)

                Author information
                https://orcid.org/0000-0001-8512-8676
                Article
                Publisher ID: INA12899
                DOI: 10.1111/ina.12899
                PMC ID: 8447035
                PubMed ID: 34181766
                SO-VID: 94709596-1b21-40e5-abc4-c383ffae755e
                Copyright © ©2021 John Wiley & Sons Ltd.
                License:

                This article is being made freely available through PubMed Central as part of the COVID-19 public health emergency response. It can be used for unrestricted research re-use and analysis in any form or by any means with acknowledgement of the original source, for the duration of the public health emergency.

                History
                Date revision received : 20 May 2021
                Date received : 24 February 2021
                Date accepted : 12 June 2021
                Page count
                Figures: 2, Tables: 3, Pages: 10, Words: 17845
                Funding
                Funded by: National Natural Science Foundation of China , doi 10.13039/501100001809;
                Award ID: 51778520
                Funded by: Beijing Tsinghua Changgung Hospital
                Award ID: 12020Z1003
                Categories
                Subject: Original Article
                Subject: Original Articles
                Custom metadata
                source-schema-version-number 2.0
                edited-state corrected-proof
                details-of-publishers-convertor Converter:WILEY_ML3GV2_TO_JATSPMC version:6.0.7 mode:remove_FC converted:17.09.2021

                ScienceOpen disciplines: Health & Social care
                Keywords: carbon dioxide,covid‐19,nosocomial infection,ventilation
                Data availability:
                ScienceOpen disciplines: Health & Social care
                Keywords: carbon dioxide, covid‐19, nosocomial infection, ventilation

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