06/02/2020
Hot Yoga Studios planning to reopen, helpful COVID-19 info:
Scientific studies suggest high-humidity and heat are associated with inactivation of airborne viruses such as coronaviruses.
“Based on data from more than 3,700 locations around the world from December through April, the team found that infection rates start to fall off with temperatures over 77 degrees, with very high levels of bright sunlight and with rising humidity (Freeman, 2020).”
“Low humidity and temperature environment would promote the viability of SARS-CoV-2 in the droplets and impaired ciliary clearance and innate immune defense, for robust access to the deep lung tissue and rapid transmission between infected individuals (Moriyama, Hugentobler, & Iwasaki, 2020).”
High humidity slows the airborne movement of coronavirus. “...Flu viruses spread more easily in colder temperatures. It's got to do with the relative humidity of the air going down as the temperature drops, and then there's less moisture in the air and these respiratory viruses move through the air more easily (Beaubien, 2020).”
Increased heat and humidity vs. coronavirus: “Increasing the temperature and humidity of potentially contaminated indoor spaces appears to reduce the stability of the virus (Freedman & Samenow, 2020).”
Effect on stability of coronavirus at 86° or more: “At a temperature of 30°C [86°F] or more the duration of persistence [of Coronaviruses] is shorter (Kampf, Todt, Pfaender, & Steinmann, 2020).”
Viral decay: “Increased temperature and humidity have both been shown to increase the rate of respiratory viral decay (Wilson, Norton, Young, & Collins, 2020).”
Viruses inactivated in heat. “Both viruses were inactivated more rapidly at 40°C than at 20°C (Casanova, Jeon, Rutala, Weber, & Sobsey, 2010).”
“Maintaining airborne moisture levels that reduce survival of the virus in the air and on surfaces could be another tool for managing public health risks of influenza (Myatt et al., 2010).”
Seasonality of viruses: “This seasonal cycle is consistent with a wintertime [low heat and humidity] increase in IVS and IVT [viruses] and may explain the seasonality of influenza (Shaman & Kohn, 2009).”
Viruses remain viable longer in an airborne state at low humidity. “The results suggest that TGEV [virus], and perhaps other coronaviruses, remain viable longer in an airborne state and are sampled more effectively at low RH [Relative Humidity] than at high humidity (Kim, Ramakrishnan, Raynor, & Goyal, 2007).”
Viruses show low survival in high humidity in 9 studies. “…relative humidity can affect the incidence of respiratory infections and allergies. Experimental studies on airborne-transmitted infectious bacteria and viruses have shown that the survival or infectivity of these organisms is minimized by exposure to relative humidities between 40 and 70%. Nine epidemiological studies examined the relationship between the number of respiratory infections… (Arundel, Sterling, Biggin, & Sterling, 1986).
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Shaman, J., & Kohn, M. (2009). Absolute humidity modulates influenza survival, transmission, and seasonality. Proceedings of the National Academy of Sciences, 106(9), 3243-3248. doi:10.1073/pnas.0806852106
Wilson, N. M., Norton, A., Young, F. P., & Collins, D. W. (2020). Airborne transmission of severe acute respiratory syndrome coronavirus‐2 to healthcare workers: A narrative review. Anaesthesia. doi:10.1111/anae.15093
Casanova, L. M., Jeon, S., Rutala, W. A., Weber, D. J., & Sobsey, M. D. (2010). Effects of Air Temperature and Relative Humidity on Coronavirus Survival on Surfaces. Applied and Environmental Microbiology, 76(9), 2712-2717. doi:10.1128/aem.02291-09
Arundel, A. V., Sterling, E. M., Biggin, J. H., & Sterling, T. D. (1986). Indirect Health Effects of Relative Humidity in Indoor Environments. Environmental Health Perspectives, 65, 351. doi:10.2307/3430203
Kim, S. W., Ramakrishnan, M. A., Raynor, P. C., & Goyal, S. M. (2007). Effects of humidity and other factors on the generation and sampling of a coronavirus aerosol. Aerobiologia, 23(4), 239-248. doi:10.1007/s10453-007-9068-9
Myatt, T. A., Kaufman, M. H., Allen, J. G., Macintosh, D. L., Fabian, M. P., & Mcdevitt, J. J. (2010). Modeling the airborne survival of influenza virus in a residential setting: The impacts of home humidification. Environmental Health, 9(1). doi:10.1186/1476-069x-9-55
Beaubien, J. (2020, April 24). Will Heat And Humidity Kill The Coronavirus? Retrieved May 30, 2020, from https://www.npr.org/2020/04/24/843529615/will-heat-and-humidity-kill-the-coronavirus
Freedman, A., & Samenow, J. (2020, April 24). White House promotes new lab results suggesting heat and sunlight slow coronavirus. Retrieved May 30, 2020, from https://www.washingtonpost.com/weather/2020/04/23/lab-study-coronavirus-summer-weather/
Freedman, H., (6/2/20 AT 5:30 AM EDT) The Right Level of Humidity May Be Important Weapon in Fighting Coronavirus, New Studies Show. Retrieved June 2, 2020 from https://www.newsweek.com/right-level-humidity-may-important-weapon-fighting-coronavirus-new-studies-show-1507947
Kampf, G., Todt, D., Pfaender, S., & Steinmann, E. (2020). Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents. Journal of Hospital Infection, 104(3), 246-251. doi:10.1016/j.jhin.2020.01.022
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Compiled by Philip Urso, philip@urso.com.
Disclosure: Urso is co-owner of a heated yoga studio. He researched virus data to learn, in addition to State of Rhode Island and Federal guidelines, the safety of heat and humidity in yoga classes.
Readers can reach their own conclusions and research further by reading the cited studies (many are available online) and by searching relevant keywords at scholar.google.com.
