To the Editor: A novel human coronavirus that is now named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (formerly called 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 (10 5.25 50% tissue-culture infectious dose [TCID 50 ] per milliliter) or SARS-CoV-1 (10 6.75-7.00 TCID 50 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 10 3.5 to 10 2.7 TCID 50 per liter of air. This reduction was similar to that observed with SARS-CoV-1, from 10 4.3 to 10 3.5 TCID 50 per milliliter (Fig. 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 (Fig. 1A), although the virus titer was greatly reduced (from 10 3.7 to

HCoV-19 (SARS-2) has caused >88,000 reported illnesses with a current case-fatality ratio of ~2%. Here, we investigate the stability of viable HCoV-19 on surfaces and in aerosols in comparison with SARS-CoV-1. Overall, stability is very similar between HCoV-19 and SARS-CoV-1. We found that viable virus could be detected in aerosols up to 3 hours post aerosolization, up to 4 hours on copper, up to 24 hours on cardboard and up to 2-3 days on plastic and stainless steel. HCoV-19 and SARS-CoV-1 exhibited similar half-lives in aerosols, with median estimates around 2.7 hours. Both viruses show relatively long viability on stainless steel and polypropylene compared to copper or cardboard: the median half-life estimate for HCoV-19 is around 13 hours on steel and around 16 hours on polypropylene. Our results indicate that aerosol and fomite transmission of HCoV-19 is plausible, as the virus can remain viable in aerosols for multiple hours and on surfaces up to days.

The coronavirus pandemic has created worldwide shortages of N95 respirators. We analyzed 4 decontamination methods for effectiveness in deactivating severe acute respiratory syndrome coronavirus 2 virus and effect on respirator function. Our results indicate that N95 respirators can be decontaminated and reused, but the integrity of respirator fit and seal must be maintained.

medRxiv preprint Dear editor, 10The unprecedented pandemic of COVID-19 has created worldwide shortages of personal protective 11 equipment, in particular respiratory protection such as N95 respirators(1). SARS-CoV-2 transmission is 12 frequently occurring in hospital settings, with numerous reported cases of nosocomial transmission 13 highlighting the vulnerability of healthcare workers(2). The environmental stability of SARS-CoV-2 14 underscores the need for rapid and effective decontamination methods. In general, N95 respirators are 15 designed for single use prior to disposal. Extensive literature is available for decontamination procedures 16 for N95 respirators, using either bacterial spore inactivation tests, bacteria or respiratory viruses (e.g. 17 influenza A virus)(3-6). Effective inactivation methods for these pathogens and surrogates include UV, 18 ethylene oxide, vaporized hydrogen peroxide (VHP), gamma irradiation, ozone and dry heat(3-7). The 19 filtration efficiency and N95 respirator fit has typically been less well explored, but suggest that both 20 filtration efficiency and N95 respirator fit can be affected by the decontamination method used (7, 8). For 21 a complete list of references see supplemental information. 23Here, we analyzed four different decontamination methods -UV radiation (260 -285 nm), 70ºC dry heat, 24 70% ethanol and vaporized hydrogen peroxide (VHP) -for their ability to reduce contamination with 25 infectious SARS-CoV-2 and their effect on N95 respirator function. For each of the decontamination 26 methods, we compared the normal inactivation rate of SARS-CoV-2 on N95 filter fabric to that on 27 stainless steel, and we used quantitative fit testing to measure the filtration performance of the N95 28 respirators after each decontamination run and 2 hours of wear, for three consecutive decontamination 29 and wear sessions (see supplemental information). VHP and ethanol yielded extremely rapid inactivation 30 both on N95 and on stainless steel ( Figure 1A). UV inactivated SARS-CoV-2 rapidly from steel but more 31 slowly on N95 fabric, likely due its porous nature. Heat caused more rapid inactivation on N95 than on 32 steel; inactivation rates on N95 were comparable to UV. 33 34 for use under a CC0 license.Quantitative fit tests showed that the filtration performance of the N95 respirator was not markedly 35 reduced after a single decontamination for any of the four decontamination methods ( Figure 1B). 36Subsequent rounds of decontamination caused sharp drops in filtration performance of the ethanol-treated 37 masks, and to a slightly lesser degree, the heat-treated masks. The VHP and UV treated masks retained 38 comparable filtration performance to the control group after two rounds of decontamination, and 39 maintained acceptable performance after three rounds. 41Taken together, our findings show that VHP treatment exhibits the best combination of rapid inactivation 42 of SARS-CoV-2 and preservation of N95 respirator integrity, under the experimental conditions used here 43 (...

Since emerging in late 2019, SARS-CoV-2 has caused a global pandemic, and it may become an endemic human pathogen. Understanding the impact of environmental conditions on SARS-CoV-2 viability and its transmission potential is crucial to anticipating epidemic dynamics and designing mitigation strategies. Ambient temperature and humidity are known to have strong effects on the environmental stability of viruses, but there is little data for SARS-CoV-2, and a general quantitative understanding of how temperature and humidity affect virus stability has remained elusive. Here, we characterise the stability of SARS-CoV-2 on an inert surface at a variety of temperature and humidity conditions, and introduce a mechanistic model that enables accurate prediction of virus stability in unobserved conditions. We find that SARS-CoV-2 survives better at low temperatures and extreme relative humidities; median estimated virus half-life was more than 24 hours at 10 °C and 40 % RH, but less than an hour and a half at 27 °C and 65 % RH. Our results highlight scenarios of particular transmission risk, and provide a mechanistic explanation for observed superspreading events in cool indoor environments such as food processing plants. Moreover, our model predicts observations from other human coronaviruses and other studies of SARS-CoV-2, suggesting the existence of shared mechanisms that determine environmental stability across a number of enveloped viruses.

Ambient temperature and humidity strongly affect inactivation rates of enveloped viruses, but a mechanistic, quantitative theory of these effects has been elusive. We measure the stability of SARS-CoV-2 on an inert surface at nine temperature and humidity conditions and develop a mechanistic model to explain and predict how temperature and humidity alter virus inactivation. We find SARS-CoV-2 survives longest at low temperatures and extreme relative humidities (RH); median estimated virus half-life is >24 hours at 10C and 40% RH, but ~1.5 hours at 27C and 65% RH. Our mechanistic model uses fundamental chemistry to explain why inactivation rate increases with increased temperature and shows a U-shaped dependence on RH. The model accurately predicts existing measurements of five different human coronaviruses, suggesting that shared mechanisms may affect stability for many viruses. The results indicate scenarios of high transmission risk, point to mitigation strategies, and advance the mechanistic study of virus transmission.

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The unprecedented pandemic of SARS-CoV-2 has created worldwide shortages of personal protective equipment, in particular respiratory protection such as N95 respirators. SARS-CoV-2 transmission is frequently occurring in hospital settings, with numerous reported cases of nosocomial transmission highlighting the vulnerability of healthcare workers. In general, N95 respirators are designed for single use prior to disposal. Several groups have addressed the potential for re-use of N95 respirators from a mechanical or from a decontamination perspective. Here, we analyzed four different decontamination methods – UV radiation (260 – 285 nm), 70ºC heat, 70% ethanol and vaporized hydrogen peroxide (VHP) – for their ability to reduce contamination with infectious SARS-CoV-2 and their effect on N95 respirator function.