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Survival of SARS-CoV-2 on Environmental Surfaces

Summary

Data from the U.S. National Institutes of Health shows that inocula of SARS-CoV-2 at 21-23°C (69.8-73.4°F) and 40% relative humidity (RH) remained culturable for up to 72 hours on plastic and stainless steel, for 24 hours on cardboard (simulates packaged products), and for 4 hours on copper. SARS-CoV-1 remained culturable for up to 72 hours on plastic, for 48 hours on stainless steel, and for 8 hours on either cardboard or copper. Artificially generated aerosols (nebulizer; 21-23°C [69.8-73.4°F] and 65% RH) were collected at intervals over a 3-hour period, and both viruses remained viable and detectable throughout the 3-hour duration of the experiment. Detailed experiments on variations of heat and humidity and viability in different matrices (such as nasal secretions, sputum, and fecal matter) are ongoing.

Preliminary information from WHO had simply suggested that the novel coronavirus, SARS-CoV-2 (the virus causing COVID-19), may survive for a few hours or more [1] on environmental surfaces. However, based on data gathered from experimental research and systematic reviews presented below, related zoonotic coronaviruses, SARS-CoV and MERS-CoV, have been shown to persist on various surfaces at room temperature (20-25°C [68-77°F]) for about 1 to 6 days. In contrast, under certain experimental conditions of increased temperature and humidity, the survivability of coronaviruses has been demonstrated to show a rapid decline. Despite this, no evidence in human populations exists for an effect of heat or humidity on transmission parameters.

Introduction

Respiratory viruses that are shed from nasopharyngeal secretions of infected persons may survive for extended periods on different surfaces, resulting in environmental contamination and potential transmission to other individuals [2] . To date a single high-quality study specifically details stability, environmental persistence, and survival of SARS-CoV-2 on environmental surfaces. Data on the stability of SARS-CoV and MERS-CoV may also be used as a surrogate for circumstances not yet studied for SARS-CoV-2.

Key Original Research Papers

Original data on SARS-CoV and MERS-CoV survival are summarized below.

Survival of SARS-CoV-2

Data from the U.S. National Institutes of Health [3] shows that inocula of SARS-CoV-2 at 21-23°C (69.8-73.4°F) and 40% relative humidity (RH) remained culturable for up to 72 hours on plastic and stainless steel, for 24 hours on cardboard (simulates packaged products), and for 4 hours on copper. SARS-CoV-1 remained culturable for up to 72 hours on plastic, for 48 hours on stainless steel, and for 8 hours on either cardboard or copper. Artificially generated aerosols (nebulizer; 21-23°C [69.8-73.4°F] and 65% RH) were collected at intervals over a 3-hour period, and both viruses remained viable and detectable throughout the 3-hour duration of the experiment. Detailed experiments on variations of heat and humidity and viability in different matrices (such as nasal secretions, sputum, and fecal matter) are ongoing.

Survival of SARS-CoV and MERS CoV

  • Duan and colleagues assessed the stability of SARS-CoV on surfaces and commonly used materials (including wood, glass, mosaic, metal, cloth, paper [filter and press], and plastic). Viral samples were placed on the surface of these materials and stored at room temperature (20°C [68°F]) over time. Results showed that viral infectivity for cells for samples placed on most of these materials persisted for approximately 60 to 72 hours after exposure. By day 5, low levels of infectivity were detectable from viral samples placed on metal, cloth, and filter paper but were undetectable in all the other samples [4] .
  • A similar study by van Doremalen and colleagues examined the stability of MERS-CoV on steel and plastic surfaces and adjusted their experimental variables to reflect a wide range of environmental conditions, including an indoor environment (20°C and 40% RH [relative humidity]). The conditions were categorized as follows: high temperature and low humidity (30°C [86°F] and 30% RH), high temperature and high humidity (30°C and 80% RH), and low temperature and low humidity (20 °C and 40% RH). Droplets of MERS-CoV were spotted onto the surface of steel and plastic washers that were incubated under these 3 conditions and analyzed at different time points over a 72-hour time frame. At a temperature of 20°C and 40% RH, no differences in stability could be observed between the plastic and steel surfaces after storage; MERS-CoV was stable and could be recovered 48 to 72 hours after exposure. However, for samples incubated at 30°C and 80% RH and at 30°C and 30% RH, the virus remained viable for only 8 hours and 24 hours, respectively [5] .
  • Chan and colleagues assessed the stability of SARS-CoV on smooth surfaces at different temperatures and RH. The virus was placed in individual wells of a 24-well plastic plate, dried, incubated under different conditions, and assessed for residual viral infectivity at different time points. Under conditions mimicking room temperature (22-25°C [71.6-77.0°F]) and RH of a typical air-conditioned room (40%–50%), SARS-CoV that was dried on plastic retained viability for up to 5 days, after which infectivity gradually declined over time [6] .
  • Rabenau and colleagues examined the in vitro stability of different coronaviruses, including SARS-CoV. Infected cell culture supernatants were applied to a plastic surface (polystyrene petri dishes) and incubated at room temperature, either in a suspension or in a dried state. Residual infectious titers were assessed at different time points during a 9-day period. Infectious titers of all viruses tested declined over time. Results indicated that infectivity of SARS-CoV in a dried state persisted beyond 6 days (but less than 9 days), whereas it persisted for more than 9 days in the suspension [7] .

N.B. The persistence of SARS-CoV for more than 9 days in an artificial suspension on plastic reported by Rabenau and colleagues may not be a true reflection of virus persistence on a common environmental surface because the material used was a polystyrene petri dish. Polystyrene, being a synthetic hydrocarbon polymer designed to facilitate cell culture in vitro for use in research laboratories [8] , may have contributed to artificial enhancement of survivability of SARS-CoV under these conditions.

Review Articles

Articles from 2 different systematic reviews on the persistence and survivability of pre-SARS-CoV-2 coronaviruses (including SARS-CoV and MERS-COV) on a wide variety of inanimate surfaces were also analyzed, and key findings are summarized below.

  • In the article by Krame and colleagues (assessing the persistence of nosocomial pathogens), the authors suggest that most clinically relevant respiratory tract viruses can persist on inanimate surfaces for a few days and reported a duration of persistence of 72 to 96 hours in serum, diluted sputum, and feces for SARS-CoV [9] .
  • A more recent systematic review article by Kampf and colleagues analyzed results from 22 research articles and tabulated the duration of persistence of different coronaviruses (including SARS-CoV and MERS-CoV) on several inanimate surfaces, such as glass, metal, and plastic. Reported data on virus persistence were varied and dependent on viral titer and strain as well as on the environmental conditions and surface characteristics. At room temperature (20-25°C), viral persistence of MERS-CoV on plastic and on steel was 48 hours; for SARS-CoV, persistence of 4 to 9 days (9 days based only on Rabenau above) was reported for plastic; 4 days on wood; 5 days on metal; less than 5 minutes to 5 days on paper; 4 days on glass; and 1 hour to 2 days on a disposable gown [10] .

Conclusion

In summary, based on results from the studies reviewed above, SARS-CoV-2 remained culturable for up to 72 hours on plastic and stainless steel, for 24 hours on cardboard (simulates packaged products), and for 4 hours on copper. Artificially generated aerosols were collected at intervals over a 3-hour period, and SARS-CoV-2 remained viable and detectable throughout the 3-hour duration of the experiment. Detailed SARS-CoV-2 experiments on variations of heat and humidity and viability in different matrices (such as nasal secretions, sputum, and fecal matter) are ongoing. Using other coronaviruses as a surrogate, the survival rate of zoonotic coronaviruses on different inanimate/environmental surfaces ranges from 1 to 6 days and depends on numerous factors, such as ambient temperature, relative humidity, type of bodily fluid contaminating the surface, the environmental surface itself, and whether the virus is in a liquid or dry state.

Footnotes
  1. ^ World Health Organization: Q & A on coronaviruses. [February 12, 2020]. Available from: https://www.who.int/news-room/q-a-detail/q-a-coronaviruses
  2. ^ Sizun J, Yu MW, Talbot PJ. Survival of human coronaviruses 229E and OC43 in suspension and after drying on surfaces: a possible source of hospital-acquired infections. J Hosp Infect. 2000;46(1):55-60.
  3. ^ medRxiv preprint doi: van Doremalen N, Bushmaker T, Morris D. et al, Aerosol and surface stability of HCoV-19 (SARS-CoV-2) compared to SARS-CoV-1. medRxiv 2020.03.09.20033217.
  4. ^ Duan SM, Zhao XS, Wen RF et al. Stability of SARS coronavirus in human specimens and environment and its sensitivity to heating and UV irradiation. Biomed Environ Sci. 2003;16(3):246-55.
  5. ^ Van Doremalen N, Bushmaker T, Munster VJ. Stability of Middle East respiratory syndrome coronavirus (MERS-CoV) under different environmental conditions. Euro Surveil. 2013;18(38):20590.
  6. ^ Chan KH, Peiris JS, Lam SY, Poon LL, Yuen KY, Seto WH. The effects of temperature and relative humidity on the viability of the SARS coronavirus. Adv Viro. 2011;2011:734690.
  7. ^ Rabenau HF, Cinatl J, Morgenstern B, Bauer G, Preiser W, Doerr HW. Stability and inactivation of SARS coronavirus. Med Microbiol Immunol. 2005;194(1-2):1-6.
  8. ^ Ryan JA. Evolution of cell culture surfaces. BioFiles. 2008;3(8):21.
  9. ^ Kramer A, Schwebke I, Kampf G. How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infect Dis. 2006;6(1):130.
  10. ^ Kampf G, Todt D, Pfaender S, Steinmann E. Persistence of coronaviruses on inanimate surfaces and its inactivation with biocidal agents. J Hosp Infect. 2020 [Online ahead of print]. doi: 10.1016/j.jhin.2020.01.022.