key: cord-0907632-49ty6kqh authors: Seo, Minjeong; Lim, Hakmyeong; Park, Myungkyu; Ha, Kwangtae; Kwon, Seungmi; Shin, Jinho; Lee, Jaein; Hwang, Youngok; Oh, Younghee; Shin, Yongseung title: Field study of the indoor environments for preventing the spread of the SARS‐CoV‐2 in Seoul date: 2021-11-21 journal: Indoor Air DOI: 10.1111/ina.12959 sha: 144b8428e15027b45a7d32201903667f7bab15b7 doc_id: 907632 cord_uid: 49ty6kqh Despite the prolonged global spread of COVID‐19, few studies have investigated the environmental influence on the spread of SARS‐CoV‐2 RNA with a metropolitan scale, particularly the detection of SARS‐CoV‐2 after disinfection at multi‐use facilities. Between February 2020 and January 2021, 1,769 indoor air samples and object surfaces were tested at 231 multi‐use facilities where confirmed cases were known to have occurred in Seoul, to determine whether SARS‐CoV‐2 RNA could be detected even after disinfection. Samples were collected by air scanner and swab pipette and detected by real‐time RT‐PCR. As a result, 10 (0.56%) positive samples were detected despite disinfection. The common environmental features of all 10 were surfaces that contained moisture and windowless buildings. With the aim of preventing the spread of COVID‐19, from January to February 2021, we next conducted 643 preemptive tests before the outbreak of infections at 22 multi‐use facilities where cluster infections were frequent. From these preemptive inspections, we obtained five (0.78%) positive results from two facilities, which enabled us to disinfect the buildings and give all the users a COVID‐19 test. Based on the study purpose of finding and investigating cases of positive detection even after disinfection in the field through long‐term environmental detection in a large city, our preemptive investigation results helped to prevent the spread of infectious diseases by confirming the potential existence of an asymptomatic patient. the cell culture method takes 3-4 days to cultivate and 72 h to confirm after inoculation, resulting in a minimum of 6 days for confirmation, 20 compared to within 24 h after sampling for RT-PCR. Cell culture is not suitable for rapid response or for large sample sizes. In addition, the difficulty in obtaining a recoverable SARS-CoV-2 cell culture sample hinders its application to field investigations. 21 In order to quickly reopen facilities used by an unspecified number of people, it is necessary to consider both certainty and efficiency. RNA detection via RT-PCR within 24 h, including pretreatment, is faster than the virus culture method that can clearly confirm whether the virus remaining in the environmental sample can cause secondary infections of people. If environmental samples tested negative for SARS-CoV-2 RNA, the facility can be safely reopened for use. Using real-time RT-PCR to quickly respond to target facilities will reduce the social costs arising from prolonged closure. Some facilities simply cannot be closed for extended periods, such as apartments, public transportation, and large hospitals. In particular, the closure of large hospitals for an extended period will lead to a shortage of medical institutions capable of treating emergency patients. 22 Furthermore, it is necessary to check the effectiveness of disinfection through viral RNA testing to ensure the safety and health of citizens. Thus, environmental RNA detection can be a strategy to track and monitor the rate of viral spread in communities and to suggest preventive measures. 7, 8, 23, 24 People spend more than 90% of the day indoors, 5, 43 and viral infections are easily transmitted and acquired, especially in crowded and poorly ventilated indoor environments. 25 The second transmission route is the spread of the virus through inanimate surface contact arising from touching droplet-coated objects with the hands and then touching the eyes, nose, or mouth. 7 Again, this route can be blocked by testing all object surfaces for the SARS-CoV-2 virus and responding appropriately such as closing, disinfecting, ventilating, and cleaning. The third is air transmission in which aerosol particles containing viruses are widely spread in the air and thus infect non-infected persons. A non-infected person can even be infected by entering an enclosed room with inadequate ventilation from which an infected person has just exited from. 29, 30 The virus attached to the aerosol can be captured through inhaling the air in the room by an air scanner. Transmission can then be prevented by testing for the presence of the virus and responding appropriately. The present study has three goals. First, by conducting a longterm environmental investigation of SARS-CoV-2 RNA in numerous multi-use facilities in Seoul, we specifically identified those facilities with positive results even after disinfection and are thereby able to share the common causes leading to these positive results. Second, we aim to provide a protocol that can ensure the safety of citizens and can enable the target facility to be reopened rapidly by clearly confirming the presence of environmental contamination of the virus on surfaces and in the air. Finally, we suggest a plan to prevent the spread of cluster infections in multi-use facilities by identifying • A metropolitan-scale investigation was conducted on the environmental contamination of SARS-CoV-2 RNA over a year in Seoul. • SARS-CoV-2 RNA was detected on the object surfaces several days after disinfection, and most of the positive samples were collected on the surfaces containing moisture in indoor environments that were not well ventilated. • Based on testing at 231 multi-use facilities in the field, this study presented a protocol for safely reusing such facilities by confirming whether there is environmental contamination by virus RNA after disinfection. • A preemptive investigation of environmental contamination of the virus helped to prevent the spread of the infectious disease by identifying the potential existence of asymptomatic patients. the potential existence of any pre/asymptomatic users of the facilities through a preemptive investigation of environmental contamination of the virus. The WHO proposed a practical protocol for collecting environmental samples in hospitals and homes where COVID-19 patients have stayed. 32 Based on this, we extended the range of the environmental sample tests to public multi-use facilities. During February-April 2020, we conducted a full investigation of such multi-use facilities ( Table 2 ) that we could obtain consent from the owners. As no SARS-CoV-2 RNA signal was detected in any environmental samples for the first three months, only the facilities requested by the owners or multi-use facilities with cluster infections were examined after May. A cross-sectional study design was used for detecting viruses in the indoor environment in order to check the safety of the target facilities that pre/asymptomatic persons had visited from February 2020 to January 2021. The procedure for conducting this investigation is shown in Figure 1 . As shown in SI 1-4, the number of daily confirmed cases increased explosively between February and March 2020 in regions other than Seoul. According to SI 4, the daily number of confirmed cases in Seoul was between 0 and 30 before mid-August, and then subsequently rising to more than 100, with this increase being attributed to summer holidays. The onset of winter led to a further increase to more than 1,000 confirmed daily cases (SI 2-4). As the increase seen during the August holiday season revealed a possibility of an exponential increase in case numbers over the Lunar (Chinese) New Year's holiday in February, so a preliminary inspection was needed to prevent the increase. A preemptive inspection study was carried out according to the procedure shown in Figure 2 . We selected 22 multi-use facilities that were frequent sites of group infections, such as call centers, nursing facilities, logistics centers, and homeless facilities (Table 4 ). The surface samples included all surfaces reported as having been which is a portable and easy-to-use air sampling instrument for the collection of airborne viruses. 33 The air scanner was equipped with a disposable gelatin membrane filter (Sartorius Stedim Biotech, Germany) to capture viruses floating in the air. The aerosol collection device was installed at a height of 1.5 m and used to take two separate samples with an air intake flow rate of 50 L/min for 20 min. 34 All samples were shipped at 4°C in cooler bags prior to transfer to a laboratory. Samples were immediately processed in biosafety level 2 or 3 (BLS-2 or BLS-3) laboratories and directly analyzed. A BSL-2 laboratory deals with agents associated with human diseases that pose a moderate health hazard. 46 The SARS-CoV-2 RNA was detected in the staff lounge of the D subway station, which was included as public transportation, but it was a restricted area that was only available to employees and inaccessible to public transportation users. Investigation procedure for multi-use facilities with confirmed cases between February 2020 and January 2021 in Seoul Surface samples collected by swab included buffer peptone water broth (Pipette Swab Plus + , 3 M, USA). Before RT-PCR, buffer solutions of swab samples were vortexed for 1 min. 35 Samples (270 ul) were put into 270 ul of lysis buffer and reacted at room temperature for 10 min before 500 ul was added to the processing cartridge, and extracted with a MagNA Pure 96 (Roche, Penzberg, Germany) machine. Virus detection was carried out by analyzing the presence of viral The public-use facilities inspected included 51 restaurants, 33 hospitals, 32 business sites, including call centers and offices, 31 public transportation areas, 25 pharmacies, and 20 marts ( returned a positive detection result for viral RNA, even after disinfection (Table 2) . Ct values of all positive samples are shown in Figure 3 . Cases (1-4) of SARS-CoV-2 RNA detection even after disinfection are specifically described (Table 3 ). (Table 3) . Notably, this towel was still wet when collected for testing. Following our immediate notification of the positive result, the lounge was disinfected twice more and was kept closed. On September 29, 24 surface samples, including the towel in the shower room, were re-examined and all were negative. The daily confirmed cases in Korea surpassed 1,000 and in Seoul surpassed 500 in mid-December 2020 (SI 3-4). This rapid increase in the number of confirmed cases necessitated a preemptive response in early January in preparation for the February holiday. For preemptive inspections, as shown in Table 4 (Figure 4) , on a folded blanket ( Figure 5 ) in the sleeping room. Since 0.58% of the surface samples remained positive even after disinfection as above, note that this is a study result (Table 2) , there is value in trying to identify any commonality among these positivetesting surfaces. All four positive surface samples were drains in Apartment case C, and the drains were located in windowless bathrooms. Drains are usually contaminated and wet environments. The virus RNA at Subway Station D was detected in the windowless staff shower room. Even though this shower room was disinfected and samples were taken two days later, the towel hung on a hanger was still wet. The C and D locations were both windowless bathrooms with no natural ventilation. In the case of call center A, RNA was detected two days later after disinfection in the sponge part of the headset microphone for phone calls, and this porous material only dries after an extended period (Table 4 ). Studies have shown that SARS-CoV-2 is more stable on a smooth surface than on a porous surface, 7,10,12,47 and it is more stable in a dry environment. 4,10-12 Biryukov et al reported that the SARS-CoV-2 of viabilities and airborne survival times expected at lower humidity levels. 11 Nevertheless, RNA was detected even after disinfection on the wet headset sponge, the four drains, and the wet towel (Table 3) . When disinfecting contaminated surfaces, it is necessary to keep the contact times, which are times during which they must be visibly wet. 39 If RNA is detected on the surface of a moisture object even a few days after disinfection, it is difficult to confirm that it has been (1), toilet sink (7), toilet (14), shower (6), mattress (4), sleeping room locker (9), blanket (2), wall (2), bag (2), TV (1), home appliance (1) enters the facility. 13 Therefore, it is necessary to find a balance between the SARS-CoV-2 risk and the human risk of the disinfectant. The protocol presented in Figure 1 is According to Alicia et al, the success rate of detecting SARS-CoV-2 increases if the air suction flow rate is increased in a space with a COVID-19 patient. 42 Since this field study was conducted after the cases had been confirmed, the effects of temperature and humidity conditions and of air intake flow rate could not be investigated as a laboratory study would allow. The RT-PCR method was chosen rather than culture that can clearly confirm the infectivity of the virus because this study aimed to secure rapid safety against infectious diseases in a huge city. The of preemptive investigations showed Ct values <36.5 (Figure 4 ). Another study in which SARS-CoV-2 was cultured on cotton and polyester demonstrated that the virus could not survive after the first day. 12 In Case 6, the viral RNA was detected even after 12 days in a blanket, but since survival is unknown, additional research on infectivity is necessary. For 13 months, various multi-use facilities in large cities were investigated by dividing into post-outbreak and pre-inspection. This study method enabled cases to be confirmed (Table 3) This research was supported by the Seoul Metropolitan Government. Health and Environment is one of the affiliated offices of the Seoul Metropolitan Government. The authors thank Juhee Hong, Hojun Rhee, Jinsol Park Byungchul Min, and Deukhyun Yoo who helped collect the original data. The authors declare no conflict of interests. The peer review history for this article is available at https://publo ns.com/publo n/10.1111/ina.12959. Five reasons why COVID herd immunity is probably impossible Recognizing and controlling airborne transmission of SARS-CoV-2 in indoor environments Tracing surface and airborne SARS-CoV-2 RNA inside public buses and subway trains Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1 Comparative dynamic aerosol efficiencies of three emergent coronaviruses and the unusual persistence of SARS-CoV-2 in aerosol suspensions. medRxiv Public health responses to COVID-19 outbreaks on cruise ships -Worldwide Environmental detection of SARS-CoV-2 Virus RNA in health facilities in brazil and a systematic review on contamination sources Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents Clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in Wuhan Stability of SARS-CoV-2 in different environmental conditions Increasing Temperature and Relative Humidity Accelerates Inactivation of SARS-CoV-2 on Survival of SARS-CoV-2 on clothing materials SARS-CoV-2 detection rates from surface samples do not implicate public surfaces as relevant sources for transmission Virological assessment of hospitalized patients with COVID-2019 Temporal profiles of viral load in posterior oropharyngeal saliva samples and serum antibody responses during infection by SARS-CoV-2: an observational cohort study Aerosol and surface contamination of SARS-CoV-2 observed in quarantine and isolation care Severe acute respiratory syndrome coronavirus 2 RNA contamination of inanimate surfaces and virus viability in a health care emergency unit Presence and infectivity of SARS-CoV-2 virus in wastewaters and rivers SARS-CoV-2 RNA detection of hospital isolation wards hygiene monitoring during the Coronavirus Disease 2019 outbreak in a Chinese hospital Severe acute respiratory syndrome coronavirus 2 from patient with coronavirus disease, United States Ten scientific reasons in support of airborne transmission of SARS-CoV-2. The Lancet Repurposing and reshaping of hospitals during the COVID-19 outbreak in South Korea Presence of SARS-Coronavirus-2 RNA in sewage and correlation with reported COVID-19 prevalence in the early stage of the epidemic in The Netherlands Detection of SARS-CoV-2 on hospital surfaces Viral infections acquired indoors through airborne, droplet or contact transmission Indoor transmission of SARS-CoV-2. Indoor Air Detection of SARS-CoV-2 RNA residue on object surfaces in nucleic acid testing laboratory using droplet digital PCR COVID-19). How COVID-19 spreads United Nations COVID-19 Response How does COVID-19 spread? Accessed Media Resources, Press release COVID-19): A practical "how to" protocol for health care and public health professional Sampling and detection of corona viruses in air: a mini review Extensive viable Middle East Respiratory Syndrome (MERS) coronavirus contamination in air and surrounding environment in MERS isolation wards Detection of air and surface contamination by SARS-CoV-2 in hospital rooms of infected patients Disinfection Guidelines for Public-use Facilities and Multi-use Facilities 2020. 3-4th World Health Organization Cleaning and disinfection of environmental surfaces in the context of COVID-19: interim guidance Centers for Disease Control and Prevention COVID-19. Cleaning and Disinfecting Your Home. How to disinfect Decay of SARS-CoV-2 and surrogate murine hepatitis virus RNA in untreated wastewater to inform application in wastewater-based epidemiology Postnatal exposure to household disinfectants, infant gut microbiota and subsequent risk of overweight in children Airborne SARS-CoV-2 surveillance in hospital environment using high-flowrate air samplers and its comparison to surface sampling The National Human Activity Pattern Survey (NHAPS) a resource for assessing exposure to environmental pollutants Guidelines for laboratory diagnosis of coronavirus disease 2019 (COVID-19) in Korea Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR The role of environmental factors to transmission of SARS-CoV-2 (COVID-19) The data that support the findings of this study are available from the corresponding author upon reasonable request.