Should you double mask and other FAQs on airborne transmission of COVID-19

Strong evidence suggests that the SARS-CoV-2 virus is primarily airborne, what does this mean and do we change the way we protect ourselves?
A couple walking on the road, both wearing masks. The man is dressed in black, the woman is wearing red pants.
A couple walking on the road, both wearing masks. The man is dressed in black, the woman is wearing red pants.

A recent report in the medical journal The Lancet, gave scientific evidence to support that the SARS-CoV-2 virus, that has caused the COVID-19 pandemic, could be primarily airborne. In the study, six experts from the US, UK and Canada, said, “There is consistent, strong evidence that SARS-CoV-2 spreads by airborne transmission. Although other routes can contribute, we believe that the airborne route is likely to be dominant.”

To support their case the team highlighted ten scientific reasons. This included super-spreader events that “account for substantial SARS-CoV-2 transmission.” This, they said, is consistent with airborne spread of SARS-CoV-2 and couldn’t be explained by droplets or fomites (fomites are surfaces and objects contaminated by droplets expelled by infected individuals). The report also mentioned long range transmission of the virus between people quarantined in adjacent rooms in a hotel, who had never been in contact with each other. “SARS-CoV-2 has been identified in air filters and building ducts in hospitals with COVID-19 patients; such locations could be reached only by aerosols,” was another piece of evidence the Lancet study raised to corroborate its theory.

Respiratory infectious diseases can be spread in two ways–either through aerosols suspended in air or droplets. If it is transmitted in the former way, the disease is considered airborne. According to The BMJ, “Aerosols are tiny liquid particles from the respiratory tract that are generated when someone exhales, talks, or coughs, for example. They float in the air and can contain live viruses, such as measles and chickenpox.”  Both are highly infectious diseases that are classified as airborne as they are known to be spread by aerosols.

According to Dr Jacob John, who formerly headed ICMR’s Centre for Advanced Research in Virology, and Christian Medical College (CMC), Vellore professor emeritus, calling a virus airborne is just a matter of definition. “If you didn’t get a disease via say a mosquito bite or through contact with fecal matter, but the virus entered your system through your nostril then it has to be airborne,” says Dr Jacob John speaking to TNM.

He cites the example of Influenza which is usually transmitted via droplets “In some cases the droplets get smaller and smaller, these can be called aerosols which can travel a certain distance and infect someone,” says Dr John. According to him the SARS-CoV-2 virus for a short period of time and for a short distance is airborne. “So, it is a matter of gradation between droplet infection and airborne infection,” he adds.

Now that we know that the SARS-CoV-2 virus could primarily be airborne, what does this mean? Do we have to change the way we protect ourselves from the virus?

“We have had a year’s experience with the virus and have learnt more about it,” says Dr Shahid Jameel, a virologist and the Director of the Trivedi School of Biosciences at Ashoka University, speaking to TNM. “It isn’t that the behaviour of the virus has changed, it is not that it wasn’t airborne before and now is.” He says that based on the spread of the virus and studying it further, it is now known that it possibly spreads through aerosols.

“When people hear the word airborne they think if they step out their house the virus will catch them, it is nothing like that,” says Dr Jameel. “If you are indoors where the air is being recirculated and there is somebody else in the room who is shedding virus, you are likely to get it.”

Both doctors agree that the best way to protect yourself from the coronavirus continues to be wearing masks and improving the air circulation in closed spaces. “If you are in an office space or  in a closed room with people whose antecedents you don’t know, it is very important to wear a mask and keep the windows open,” says Dr Jameel.

Is there a particular mask that needs to be used? “If you are walking in a COVID-19 ward, then yes you need an N-95 mask,” says Dr John. “But for regular people most masks will do, you can use a surgical mask or even a double-layered or triple-layered cloth mask. Anything that will hold dust particles and keep it from getting into your nostrils.”

The point is to wear the mask in the right way stresses Dr Jameel. “If worn properly, covering the nose and mouth, then even a double or triple-cloth mask will provide enough protection,” he says.

Dr Jameel adds that while double masking is more efficient it isn’t always necessary. Though if your mask is flimsy then you definitely need to double mask. “Hold your mask up against light,” says Dr Jameel. “If light can be seen through it, then you need to add another layer.”

Moreover, it is very important that everyone wears a mask– infected or otherwise. “If an infected person does not know he or she has the virus but is wearing a mask, they will stop a droplet or aerosol getting into the air and infecting others,” says Dr John. 

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