A new pre-print study offers some preliminary evidence that the virus that causes COVID-19 loses most of its infectivity after 20 minutes in the air.
Uncensored UK research measured the stability of SARS-CoV-2 in aerosol droplets from five seconds to 20 minutes.
After 20 minutes, the researchers say the infectivity of SARS-CoV-2 drops to about 10% of where it started, with a large portion of that loss occurring within the first five minutes after when sprayed with aerosols.
The article is a pre-print and has not been censored, which means it has not been evaluated by the medical community for any potential errors or inaccuracies.
The data suggest that dry air may help limit overall exposure to SARS-CoV-2, the researchers say, although more research is needed to confirm this, as well as the possible effect. presence of pH and CO2 concentrations.
The study also based most of its measurements on versions of SARS-CoV-2 isolated early in the pandemic, including Alpha. However, it found no significant difference between the three variants that were used.
“Although the current general consensus is that the half-life of SARS-CoV-2 in the aerosol phase is between 1-2 hours, if not longer, we report a rapid decrease in initial infectivity within seconds to minutes after aerosol generation,” the study’s authors wrote.
“Under all measured conditions, the majority of SARS-CoV-2 was inactivated within 10 minutes of aerosolization. Further research is needed to determine how long the remainder persists and this may be the case. depends on how much the viral load is in the aerosol.”
The transmission of droplets containing SARS-CoV-2 has led to ongoing discussions around ventilation, face covering, and social distancing, with reports varying on how long the virus can be in the form of aerosols or aerosols. suspended in the air.
The length of time that SARS-CoV-2 can survive has been examined since the early days of the pandemic.
The Public Health Agency of Canada says SARS-CoV-2 is spread from person to person through respiratory droplets, which can range in size from large droplets that fall to the ground within seconds or minutes to droplets. Small particles, sometimes called aerosols, exist in the air especially indoors.
Information released in May 2020 by the UK’s Research and Innovation Foundation states that SARS-CoV-2, like many respiratory viruses, is primarily spread between people through droplets. small secretions from the nose or mouth of an infected person.
At the time, it said the half-life, or the amount of time it takes for 50% of the virus to become non-infectious, in dropper aerosols was just over an hour, with some surviving for three hours. or more.
In the spring of 2021, scientists and doctors increasingly came to the conclusion that aerosols were the main mode of transmission of SARS-CoV-2.
The latest UK study used a technique known as CELEBS, or Controlled Electrodynamic Vibration, and extracted biomolecules onto a substrate, which involved suspending the particles. contain the virus under controlled conditions. The beads were then plated onto cell culture medium.
The researchers found that the infectivity of SARS-CoV-2 at low relative humidity, or 40%, decreased almost immediately to an average of 54% within 5 seconds.
This was followed by a period of relative stability, dropping to an average of 19% after 5 minutes.
In conditions of high relative humidity of 90%, the likelihood of infection after aerosol spraying gradually decreased to 48% within the first five minutes.
In both situations, infectivity appeared to stabilize after 10 min before reaching similar points at 20 min.
The data are consistent with the view that the virus mainly spreads over short distances, the researchers say.
“The rapid loss of infectivity demonstrated in these measurements provides an alternative explanation for the short transmission distances, with the rapid loss of airborne virus infectivity making the potential for rapid transmission of the virus less likely. transmission decreases as distance from the source of the particle increases, even if the virus-carrying particles are small and can travel long distances,” the study said.
Regarding CO2, the researchers say elevated levels are indicative of a space with high density and poor ventilation, which can create conditions where SARS-CoV-2 is more stable in the air. They suggest that CO2 monitors could be of value in assessing the relative risks of indoor environments.
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