Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has emerged as a serious threat to human health worldwide. Efficient disinfection of surfaces contaminated with SARS-CoV-2 may help prevent its spread. This study aimed to investigate the in vitro efficacy of 222-nm far-ultraviolet light (UVC) on the disinfection of SARS-CoV-2 surface contamination. Methods: We investigated the titer of SARS-CoV-2 after UV irradiation (0.1 mW/cm 2) at 222 nm for 10-300 seconds using the 50% tissue culture infectious dose (TCID 50). In addition, we used quantitative reverse transcription polymerase chain reaction to quantify SARS-CoV-2 RNA under the same conditions. Results: One and 3 mJ/cm 2 of 222-nm UVC irradiation (0.1 mW/cm 2 for 10 and 30 seconds) resulted in 88.5 and 99.7% reduction of viable SARS-CoV-2 based on the TCID 50 assay, respectively. In contrast, the copy number of SARS-CoV-2 RNA did not change after UVC irradiation even after a 5-minute irradiation. Conclusions: This study shows the efficacy of 222-nm UVC irradiation against SARS-CoV-2 contamination in an in vitro experiment. Further evaluation of the safety and efficacy of 222-nm UVC irradiation in reducing the contamination of real-world surfaces and the potential transmission of SARS-CoV-2 is needed.

No abstract

SARS-CoV-2, the pathogen that causes COVID-19, originated from around Wuhan in China and has spread worldwide, causing a pandemic (WHO, 2020) . People's lives have changed dramatically due to the incorporation of measures for infection prevention. Together with the use of masks for preventing droplet infection, hand washing and hand disinfection for prevention of contact infection have become a part of daily life. Alcohol, especially diethyl alcohol, is used for hand disinfection. An ethanol content of 62-71% was reported in a review article to be effective against SARS-CoV, which is very closely related to SARS-CoV-2 (Kampf et al., 2020) . The included formulations of hand rinses were shown to be effective against SARS-CoV-2 (Kratzel et al., 2020;Suchomel et al., 2020) . On the other hand, Kratzel et al. (2020) examined ethanol concentrations and showed that ethanol at a lower concentration of 30% (v/ v) was effective against SARS-CoV-2 in the presence of 0.03% bovine serum albumin. Ethanol was also found to be effective and fast-acting in a 30-second treatment (Kratzel et al., 2020) .We examined ethanol concentrations that showed an inhibitory effect on SARS-CoV-2 to determine whether the virus can be inactivated at low ethanol concentrations. Effects of ethanol on other envelope viruses, including influenza virus, rhabdovirus and paramyxovirus, were also studied.The 2019-nCoV/Japan/AI/I-004/2020 strain of SARS-CoV-2 (provided by Dr. Makoto Takeda, the National Institute of Infectious Diseases, Japan) was propagated in VeroE6/TMPRSS2 cells (purchased from the Japanese Collection of Research Bioresources; JCRB1819) in the P3 facility of Hiroshima University. Antiviral activity measurement was based on ATSM E1052-11 as previously described (Ueda et al., 2013) . The virus (10 µl) and an ethanol solution (90 µl) were mixed. After reaction for 3 min at room temperature, infectious titers were measured by the standard TCID 50 method using the Behrens-Kraber algorithm (Karber, 1931) . Ethanol was prepared ＊

Since understanding molecular mechanisms of SARS-CoV-2 infection is extremely important for developing effective therapies against COVID-19, we focused on the internalization mechanism of SARS-CoV-2 via ACE2. Although cigarette smoke is generally believed to be harmful to the pathogenesis of COVID-19, cigarette smoke extract (CSE) treatments were surprisingly found to suppress the expression of ACE2 in HepG2 cells. We thus tried to clarify the mechanism of CSE effects on expression of ACE2 in mammalian cells. Because RNA-seq analysis suggested that suppressive effects on ACE2 might be inversely correlated with induction of the genes regulated by aryl hydrocarbon receptor (AHR), the AHR agonists 6-formylindolo(3,2-b)carbazole (FICZ) and omeprazole (OMP) were tested to assess whether those treatments affected ACE2 expression. Both FICZ and OMP clearly suppressed ACE2 expression in a dose-dependent manner along with inducing CYP1A1. Knock-down experiments indicated a reduction of ACE2 by FICZ treatment in an AHR-dependent manner. Finally, treatments of AHR agonists inhibited SARS-CoV-2 infection into Vero E6 cells as determined with immunoblotting analyses detecting SARS-CoV-2 specific nucleocapsid protein. We here demonstrate that treatment with AHR agonists, including FICZ, and OMP, decreases expression of ACE2 via AHR activation, resulting in suppression of SARS-CoV-2 infection in mammalian cells.

No abstract

Several traditional Japanese Kampo formulas are known to have inhibitory effects on infections with viruses that cause respiratory symptoms. Although some herbs and their components have been reported to suppress SARS-CoV-2 replication in vitro, it is difficult to compare effective Kampo formulas because of the different methods used in studies. Thus, we carried out in vitro experiments on the suppression of SARS-CoV-2 infection by Kampo formulas and crude drugs used for the common cold to compare their suppressive effects on virus infection. After infecting VeroE6/TMPRSS2 cells with SARS-CoV-2, lysates of the Kampo formulas and crude drugs were added, and after 24 h, the infectious titer in the medium was measured by the TCID50 method. Maoto was the most effective among the Kampo formulas, and Ephedrae herba was the most effective among the constituent crude drugs. However, a comparison of the suppressive effects of Ephedrae herba and Kampo formulas containing Ephedrae herba showed that the suppressive effect on virus infection did not depend on the content of Ephedrae herba. Based on the results, we believe that the use of Maoto among Kampo formulas is suitable as a countermeasure against COVID-19.

Background: Approximately 5% of patients with coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 develop severe COVID-19. Severe COVID-19 requires respiratory management with mechanical ventilation and an extended period of treatment. Prolonged infectious virus shedding is a concern in severe COVID-19 cases, but few reports have examined the duration of infectious virus shedding. Therefore, we investigated the duration of infectious virus shedding in patients transferred to Hiroshima University Hospital with severe COVID-19 requiring mechanical ventilation. Methods: Nasopharyngeal swab specimens were collected and analyzed using both viral culture and reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) tests between December 2020 and February 2021. Results: Of the 23 patients tested, the proportions of those with positive test results at first specimen collection (the median number of days to first specimen collection after symptom onset was 10) on RT-qPCR and viral culture tests were 95⋅7% and 30⋅4%, respectively. All six patients with positive viral culture test results who were followed-up tested negative 24 days after symptom onset but remained positive on RT-qPCR. Viral loads based on PCR testing did not decrease over time, but those determined via culture tests decreased over time. The longest negative conversion time was observed in a dialysis patient on immunosuppressive drugs. Conclusions: This study indicated that patients with severe COVID-19 remain culture positive for ≥ 10 days after symptom onset. Additionally, immunosuppressed patients with severe COVID-19 could consider isolation for ≥ 20 days.

Ethanol is an effective disinfectant against the novel coronavirus SARS-CoV-2. However, its effective concentration has not been shown, and we therefore analyzed the effects of different concentrations of ethanol on SARS-CoV-2. When SARS-CoV-2 was treated with varying ethanol concentrations and examined for changes in infectivity, the ethanol concentration at which 99% of the infectious titers were reduced was 24.3%(w/w) [30.0%(v/v)]. For reference, ethanol susceptibility was also examined with other envelope viruses, including influenza virus, vesicular stomatitis virus in the family Rhabdoviridae, and Newcastle disease virus in the family Paramyxoviridae, and the 99% inhibitory concentrations were found to be 28.8%(w/w) [34.8%(v/v)], 24.0%(w/w) [29.2%(v/v)], and 13.4%(w/w) [16.5%(v/v)], respectively. Some differences from SARS-CoV-2 were observed, but the differences were not significant. It was concluded that ethanol at a concentration of 30%(w/w) [36.2%(v/v)] almost completely inactivates SARS-CoV-2.