Shortly after the beginning of the pandemic, extensive academic research was devoted to finding differences between the emerging SARS-CoV-2 and the prior similar strains to identify the most effective prevention and mitigation strategies. Van Doremalen et al. compared the stability of SARS-CoV-2 and SARS-CoV-1 in different environmental conditions. Namely, they tested the stability of the two viruses in aerosols and on the surfaces of plastic, stainless steel, copper, and cardboard (Van Doremalen et al. 1). Hence, the authors’ primary objective was to determine the stability and the decay rates of SARS-CoV-2 and SARS-CoV-1 in five unique environmental conditions. The authors compared SARS-CoV-2 nCoV-WA1-2020 (MN985325.1) and SARS-CoV-1 Tor2 (AY274119.3) microbes to identify the differences between the related virus strains.
In the experiment, the authors used the standard measurements of the viruses, such as titers, decay rate, and half-life. Virus titer is a metric that shows the concentration of infectious particles in a sample (Schwartz par. 1). In the current study; the authors use tissue-culture infectious dose (TCIDso) per milliliter of collection medium or per liter of air in the case of aerosols to determine virus titers (Van Doremalen et al. 3). A decay rate is a metric that shows how long it takes for the virus titers to be reduced to an insignificant level (Van Doremalen et al. 1). Lastly, a half-life is a period in which the virus concentration is reduced by 50%. To bring the experiment conditions closer to real-life counterparts, the authors created an aerosol environment using a Collision nebulizer and a Goldberg drum. These instruments are highly effective in producing an environment similar to a human respiratory tract (“Collision Nebulizer”). As a result, it allowed the authors to determine more accurate virus measurements in the aerosol environment, specifically.
In the current experiment, SARS-CoV-2 and SARS-CoV-1 demonstrated the least stability on copper and aerosols. It implies that these samples are the most destructive environmental conditions for virus strains, and the microbes’ decay rates in these mediums are the fastest. The authors stated, “On copper, no viable SARS-CoV-2 was measured after 4 hours” (Van Doremalen 1). The contender for the least stability is aerosol, but this conclusion might be inaccurate since the authors only conducted a three-hour experiment for the aerosol environment and seventy-two-hour measurements of other conditions. The idea that aerosol has the least stability is supported by other research in this field and the fact that the half-lives of the aerosol and copper environments are close (El Baz and Imziln 1). Ultimately, based on the research by van Doremalen et al., it is inconclusive whether aerosol or copper shows the least stability since their measurements are nearly identical.
The authors were able to explicitly identify the material on which SARS-CoV-2 and SARS-CoV-1 demonstrated the greatest stability – plastic. The virus titers in this environmental condition were reduced to an insignificant degree only after seventy-two hours, compared to 3/4/8/24/48-hour periods in other mediums. Moreover, the virus strains demonstrated the longest half-lives of approximately seven hours on plastic (Van Doremalen et al. 1). As a result, it is safe to assume that plastic provides the greatest stability for SARS-CoV-2 and SARS-CoV-1 among the five examined environmental conditions.
There are several limitations considering the data of the current study. First, the experiment length for the aerosol environment was significantly shorter (3 hours) than for other conditions (72 hours). This limitation makes it challenging to identify the medium with the least stability since aerosols and copper demonstrate similar measurements. The other restriction that the authors explicitly mention is the increased level of noise in the half-life estimation of virus titers on cardboard (Van Doremalen et al. 1). It implies that the standard error for this medium is significantly higher than for other conditions, and the data for SARS-CoV-1 on cardboard should be interpreted skeptically. In summary, the examined two impediments are the study’s primary limitations.
Works Cited
“Collision Nebulizer.” CH Technologies USA.
El Baz, Soraia, and Boujamâa Imziln. “Can Aerosols and Wastewater be Considered as Potential Transmission Sources of COVID-19 to Humans?” European Journal of Environment and Public Health, vol. 4, no. 2, 2020, pp. 1-6.
Van Doremalen, Neeltje, et al. “Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-Cov-1.” The New England Journal of Medicine, 2020, pp. 1-3.
Schwartz, Ethan. “How to Calculate Virus Titers.” Sciencing, 2019.