On April 16, local time, the latest issue of the New England Journal of Medicine published new findings from research by researchers from the National Institute of Allergy and Infectious Diseases, Princeton University, and the University of California, Los Angeles.
The results of the study indicate that it is possible to spread the COVID-19 virus through aerosols and vectors, because the activity and infectivity of this virus can last for 3 hours in an aerosol and last up to 3 days on the surface of certain objects.
In this study, the researchers analyzed the stability of the COVID-19 virus and SARS virus in aerosols and on the surfaces of plastics, stainless steel, copper, and cardboard. All experimental results are the average of three replicates.
Here we look at the specific experimental results:
1 aerosol
The researchers used an atomizer to create an aerosol environment containing the COVID-19 virus and SARS virus. The entire experiment lasted 3 hours, and the COVID-19 virus was still alive in the aerosol. However, its infection titer decreased from 103.5TCID50 (50% tissue culture infection dose) per liter of air to 102.7TCID50.
This result is similar to the performance of the SARS virus, whose infection titer has dropped from 104.3TCID50 per ml to 103.5TCID50.
2 Plastic and stainless steel
In the experiment on the surface of the object, the researchers kept several objects at 21 to 23 degrees Celsius and a relative humidity of 40% for 7 days.
The study found that the COVID-19 virus is more stable on plastic and stainless steel, and live virus can be detected on these surfaces within 72 hours, although the virus titer is greatly reduced.
After the COVID-19 virus was placed on the plastic surface for 72 hours, the titer per ml of medium dropped from 103.7TCID50 to 100.6TCID50. After being placed on stainless steel for 48 hours, the titer per ml of medium dropped from 103.7TCID50 to 100.6TCID50.
The SARS virus behaves similarly. After 72 hours on the plastic surface, the titer per milliliter of culture medium dropped from 103.4 to 100.7 TCID50. After being placed on stainless steel for 48 hours, the titer per ml of medium dropped from 103.6TCID50 to 100.6TCID50.
3 Copper and cardboard
Compared to plastic and stainless steel, the stability of the COVID-19 virus on copper and cardboard surfaces is reduced.
On the surface of copper, the researchers did not detect the surviving COVID-19 virus after 4 hours, and the surviving SARS virus after 8 hours.
On the cardboard surface, the researchers did not measure the surviving COVID-19 virus after 24 hours, and did not measure the surviving SARS virus after 8 hours.
4 Decay rate of two viruses
In the experiment, the researchers used the Bayesian regression model to estimate the attenuation rate of the COVID-19 virus and SARS virus. The study found that under all experimental conditions, the viral titers of both viruses showed an exponential decay.
In aerosols, COVID-19 and SARS viruses have similar half-lives (the time it takes for the concentration to fall by half), with a median estimate of about 1.1 to 1.2 hours. The median half-life of COVID-19 virus on stainless steel and plastic is approximately 5.6 hours and 6.8 hours, respectively.
In addition, the two viruses have similar half-lives on copper. On cardboard, the half-life of COVID-19 virus is longer than that of SARS virus. However, the researchers emphasized that the experimental data on the cardboard varied greatly, leading to greater standard errors.
Finally, the researchers concluded that under the experimental conditions, the stability of the COVID-19 virus is similar to the SARS virus. This suggests that the difference in epidemiological characteristics of the two viruses may be caused by other factors. These include the high viral load of the upper respiratory tract and the possibility of asymptomatic transmission of COVID-19 virus infection.
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