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Humidity and Deposition Solution Play a Critical Role in Virus Inactivation by Heat Treatment of N95 Respirators.
mSphere. 2020 10 21; 5(5)M

Abstract

Supply shortages of N95 respirators during the coronavirus disease 2019 (COVID-19) pandemic have motivated institutions to develop feasible and effective N95 respirator reuse strategies. In particular, heat decontamination is a treatment method that scales well and can be implemented in settings with variable or limited resources. Prior studies using multiple inactivation methods, however, have often focused on a single virus under narrowly defined conditions, making it difficult to develop guiding principles for inactivating emerging or difficult-to-culture viruses. We systematically explored how temperature, humidity, and virus deposition solutions impact the inactivation of viruses deposited and dried on N95 respirator coupons. We exposed four virus surrogates across a range of structures and phylogenies, including two bacteriophages (MS2 and phi6), a mouse coronavirus (murine hepatitis virus [MHV]), and a recombinant human influenza A virus subtype H3N2 (IAV), to heat treatment for 30 min in multiple deposition solutions across several temperatures and relative humidities (RHs). We observed that elevated RH was essential for effective heat inactivation of all four viruses tested. For heat treatments between 72°C and 82°C, RHs greater than 50% resulted in a >6-log10 inactivation of bacteriophages, and RHs greater than 25% resulted in a >3.5-log10 inactivation of MHV and IAV. Furthermore, deposition of viruses in host cell culture media greatly enhanced virus inactivation by heat and humidity compared to other deposition solutions, such as phosphate-buffered saline, phosphate-buffered saline with bovine serum albumin, and human saliva. Past and future heat treatment methods must therefore explicitly account for deposition solutions as a factor that will strongly influence observed virus inactivation rates. Overall, our data set can inform the design and validation of effective heat-based decontamination strategies for N95 respirators and other porous surfaces, especially for emerging viruses that may be of immediate and future public health concern.IMPORTANCE Shortages of personal protective equipment, including N95 respirators, during the coronavirus (CoV) disease 2019 (COVID-19) pandemic have highlighted the need to develop effective decontamination strategies for their reuse. This is particularly important in health care settings for reducing exposure to respiratory viruses, like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19. Although several treatment methods are available, a widely accessible strategy will be necessary to combat shortages on a global scale. We demonstrate that the combination of heat and humidity inactivates a range of RNA viruses, including both viral pathogens and common viral pathogen surrogates, after deposition on N95 respirators and achieves the necessary virus inactivation detailed by the U.S. Food and Drug Administration guidelines to validate N95 respirator decontamination technologies. We further demonstrate that depositing viruses onto surfaces when suspended in culture media can greatly enhance observed inactivation, adding caution to how heat and humidity treatment methods are validated.

Authors+Show Affiliations

Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA.Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA.Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA.Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA.Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA.Division of Infectious Diseases, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, Michigan, USA.Division of Infectious Diseases, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, Michigan, USA.Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA.Division of Infectious Diseases, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, Michigan, USA.Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA.Department of Urology, University of Michigan Health System, Ann Arbor, Michigan, USA. Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA.Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, Michigan, USA kwigg@umich.edu.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

33087516

Citation

Rockey, Nicole, et al. "Humidity and Deposition Solution Play a Critical Role in Virus Inactivation By Heat Treatment of N95 Respirators." MSphere, vol. 5, no. 5, 2020.
Rockey N, Arts PJ, Li L, et al. Humidity and Deposition Solution Play a Critical Role in Virus Inactivation by Heat Treatment of N95 Respirators. mSphere. 2020;5(5).
Rockey, N., Arts, P. J., Li, L., Harrison, K. R., Langenfeld, K., Fitzsimmons, W. J., Lauring, A. S., Love, N. G., Kaye, K. S., Raskin, L., Roberts, W. W., Hegarty, B., & Wigginton, K. R. (2020). Humidity and Deposition Solution Play a Critical Role in Virus Inactivation by Heat Treatment of N95 Respirators. MSphere, 5(5). https://doi.org/10.1128/mSphere.00588-20
Rockey N, et al. Humidity and Deposition Solution Play a Critical Role in Virus Inactivation By Heat Treatment of N95 Respirators. mSphere. 2020 10 21;5(5) PubMed PMID: 33087516.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Humidity and Deposition Solution Play a Critical Role in Virus Inactivation by Heat Treatment of N95 Respirators. AU - Rockey,Nicole, AU - Arts,Peter J, AU - Li,Lucinda, AU - Harrison,Katherine R, AU - Langenfeld,Kathryn, AU - Fitzsimmons,William J, AU - Lauring,Adam S, AU - Love,Nancy G, AU - Kaye,Keith S, AU - Raskin,Lutgarde, AU - Roberts,William W, AU - Hegarty,Bridget, AU - Wigginton,Krista R, Y1 - 2020/10/21/ PY - 2020/10/22/entrez PY - 2020/10/23/pubmed PY - 2020/11/11/medline KW - N95 KW - bacteriophages KW - coronavirus KW - decontamination KW - droplet KW - fomite KW - heat KW - humidity KW - inactivation KW - influenza KW - mouse hepatitis virus KW - respirator JF - mSphere JO - mSphere VL - 5 IS - 5 N2 - Supply shortages of N95 respirators during the coronavirus disease 2019 (COVID-19) pandemic have motivated institutions to develop feasible and effective N95 respirator reuse strategies. In particular, heat decontamination is a treatment method that scales well and can be implemented in settings with variable or limited resources. Prior studies using multiple inactivation methods, however, have often focused on a single virus under narrowly defined conditions, making it difficult to develop guiding principles for inactivating emerging or difficult-to-culture viruses. We systematically explored how temperature, humidity, and virus deposition solutions impact the inactivation of viruses deposited and dried on N95 respirator coupons. We exposed four virus surrogates across a range of structures and phylogenies, including two bacteriophages (MS2 and phi6), a mouse coronavirus (murine hepatitis virus [MHV]), and a recombinant human influenza A virus subtype H3N2 (IAV), to heat treatment for 30 min in multiple deposition solutions across several temperatures and relative humidities (RHs). We observed that elevated RH was essential for effective heat inactivation of all four viruses tested. For heat treatments between 72°C and 82°C, RHs greater than 50% resulted in a >6-log10 inactivation of bacteriophages, and RHs greater than 25% resulted in a >3.5-log10 inactivation of MHV and IAV. Furthermore, deposition of viruses in host cell culture media greatly enhanced virus inactivation by heat and humidity compared to other deposition solutions, such as phosphate-buffered saline, phosphate-buffered saline with bovine serum albumin, and human saliva. Past and future heat treatment methods must therefore explicitly account for deposition solutions as a factor that will strongly influence observed virus inactivation rates. Overall, our data set can inform the design and validation of effective heat-based decontamination strategies for N95 respirators and other porous surfaces, especially for emerging viruses that may be of immediate and future public health concern.IMPORTANCE Shortages of personal protective equipment, including N95 respirators, during the coronavirus (CoV) disease 2019 (COVID-19) pandemic have highlighted the need to develop effective decontamination strategies for their reuse. This is particularly important in health care settings for reducing exposure to respiratory viruses, like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19. Although several treatment methods are available, a widely accessible strategy will be necessary to combat shortages on a global scale. We demonstrate that the combination of heat and humidity inactivates a range of RNA viruses, including both viral pathogens and common viral pathogen surrogates, after deposition on N95 respirators and achieves the necessary virus inactivation detailed by the U.S. Food and Drug Administration guidelines to validate N95 respirator decontamination technologies. We further demonstrate that depositing viruses onto surfaces when suspended in culture media can greatly enhance observed inactivation, adding caution to how heat and humidity treatment methods are validated. SN - 2379-5042 UR - https://www.unboundmedicine.com/medline/citation/33087516/Humidity_and_Deposition_Solution_Play_a_Critical_Role_in_Virus_Inactivation_by_Heat_Treatment_of_N95_Respirators_ L2 - https://doi.org/10.1128/mSphere.00588-20 DB - PRIME DP - Unbound Medicine ER -