Previous studies have shown that various contaminated surfaces by SARS-CoV-2 can still be infectious for some time (Tharayil et al.,2022). The incubation times of human-to-human transmissions have been described between 2–10 days, facilitating the spread of SARS-CoV-2 via droplets, contaminated hands or surfaces(Kampf et al.,2020a). In this study, SARS-CoV-2 RNA is largely detected on different surfaces in the COVID-19 pediatric quarantine wards, and the environmental carriage of ORF1ab and N genes was highest in the samples from the floor, bedsheets, and bathroom. Our findings show that mild and asymptomatic COVID-19 patients can contaminate their surroundings, indicating that the isolation of asymptomatic patients at home poses a risk to their family members.
Chemical disinfectants are widely used in hospitals, and increased cleaning and disinfection of healthcare surfaces is essential for effective prevention and control of SARS-CoV-2(Choi et al.,2021). SARS-CoV-2 viral RNA has been found on environmental surfaces in hospital rooms, quarantine rooms, and other hospital settings, suggesting its potential transmission via surfaces(Aytogan et al.,2020;Kotwa et al.,2022;Santarpia et al.,2020;Wei et al.,2020;Zhou et al.,2021). Environmental surfaces may be contaminated by respiratory droplets and aerosols, as they settle from the air or through contact transfer from an infected person. Some studies have attempted to isolate viable SARS-CoV-2 from environmental surfaces using cell culture but were either unsuccessful or found weak evidence of a viable virus(Colaneri et al.,2020;Santarpia et al.,2020;Zhou et al.,2021).
It has been found that viable SARS-CoV-2 can survive on various surfaces under experimental conditions ranging from 3 h to up to more than 7 d(Chin et al.,2020;van Doremalen et al.,2020). Environmental disinfection is necessary to prevent the transmission and infection waves of COVID-19. There are many disinfectants that can effectively inactivate SARS-CoV-2(Xiao et al.,2022). Lipid solvents, including EA (> 75%), formaldehyde (> 0.7%), isopropanol (> 70%), PI (> 0.23%), and sodium hypochlorite (> 0.21%), can be used to inactivate SARS-CoV-2(Dhama et al.,2021;Talic et al.,2021). The effects of disinfectants differ according to the destruction of the viral genetic structure.
To date, various types of biocidal agents are used worldwide for disinfection against SARS-CoV2 in healthcare settings(Viana et al.,2022). H2O2 exhibits virucidal activity at 0.5% or 1% concentration and inactivates SARS-CoV-2 virus(Fantozzi et al.,2022;Kampf et al.,2020b). EA, PI, and QAC are effective disinfectants for the surface disinfection of SARS-CoV-2(Baker et al.,2020;Chin et al.,2020;O'Donnell et al.,2020). EA can easily inactivate SARS-CoV-2 by penetrating the cell and causing leakage of intracellular components, leading to cell death(Lee et al.,2022;O'Donnell et al.,2020). In this study, we evaluate the effects of different disinfectants to SARS-CoV-2 RNA instead of the virus. Meanwhile, the combinations of different disinfectants are involved to further clarify the combing effects of disinfectants.
SARS-CoV-2 RNA was recently detected in feces, predicting its potential transmission via the fecal–oral route(Jones et al.,2020). A study published by Yeo et al. confirmed the possible transmission of SARS-CoV-2 via the fecal–oral route(Yeo et al.,2020). SARS-CoV-2 was firstly isolated from a stool specimen in China(Y. Zhang et al.,2020). In this study, we found that SARS-CoV-2 RNA was 100% present in the bathroom, and the CT values of bathroom samples were very low. Considering the high viral load and potential fecal–oral transmission of SARS-CoV2 in bathroom, we chose the bathroom for further study to evaluate the effectiveness of different disinfectants and combinations.
The elimination effectiveness against SARS-CoV-2 RNA varied with different types of disinfectants and their combinations. We found that low- or intermediate-effect disinfectants, including QAC, PI, EA, and CHG, could not completely degrade ORF1ab and N genes throughout the 60 min treatment. However, high-level disinfectants that bind to and react with proteins, amino acids, peptides, lipids, and nucleic acids show better clearance of SARS-CoV-2 RNA, among which H2O2, TCCA2000, and TCCA1000 destroy ORF1ab and N genes within 30 s, 30 s, and 10 min, respectively. TCCA500 presented a weaker disinfection effect on the ORF1ab and N genes, but the combination of TCCA500 with 75% EA or 0.5% PI could destroy the ORF1ab and N genes faster at 30 s and 30 min, respectively. We hypothesized that the powerful effectiveness of the combination is attributed to the synergistic effects of membrane damage and cell lysis of SARS-CoV-2 by 75% EA or 0.5% PI, and the degradation of the nucleic acid by TCCA500.
Without the exposure to disinfectants, SARS-CoV-2 RNA can be detected on the surface of some materials for a long time: One study showed that infectious virus was detectable within 48 hours in the environments, and SARS-CoV-2 RNA remained detectable for 7 days(Matson et al.,2020). Our study demonstrates that SARS-CoV-2 nucleic acid can persist for a long time in the surroundings of COVID-19 patients even if regular disinfection has been conducted. The disinfectants such as H2O2 and TCCA which directly react with nucleic acids can destroy SARS-CoV-2 RNA much faster than other disinfectants. It is noticeable that N gene can persist longer time than ORF1ab gene after disinfection using TCCA500 and combinations. Studies have demonstrated that nucleoprotein which is coded by N gene is very critical for optimal CoV genomic replication and has the ability to interfere with the host cell-cycle cellular machinery. Seemingly, the persistence of N gene in environment after some disinfection is confusing and deserve further study.