This was undoubtedly the week in which the aerial spread of the coronavirus became an important topic in the public discussion on the fight against Covid-19.
Over 200 scientists from all over the world have delivered a letter to the World Health Organization, urging her to take seriously the growing evidence that the coronavirus is transmitted through the air.
WHO he acknowledged that further research is needed “to urgently investigate such cases and assess their significance for the transmission of Covid-19”.
“I honestly don't know what people are waiting for”, he claims Chad Roy, microbiologist at Tulane University in the USA. “The WHO doesn't need to say it's an airborne disease to confirm that. In terms of scientific evidence, that's as clear as it gets.”
Airborne spread of coronavirus: is it really "airborne"?
What does “airborne” really mean in this context? It's basically a size issue. Studies seem pretty confident that SARS-CoV-2 spreads through tiny droplets that contain viral particles capable of causing an infection.
For an airborne virus, however, this has different meanings, depending on which expert you talk to. It typically means it can spread by inhaling small particles known as aerosols over long distances, perhaps even across different rooms.
This is why, when it comes to the airborne spread of Covid-19, when you ask some professionals if the virus is airborne, the answer is No. We are not seeing transmission over those types of distances.
There is debate, however, also on the meaning of "aerosol"
The droplets carrying viral particles in the air can be of any size, but while larger ones will quickly fall to the ground or other surfaces, smaller ones (just a few microns in diameter) will remain in the air for a while, risking to inhale them.
The word “aerosol” is primarily used to describe these smaller particles.
If SARS-CoV-2 is airborne, it is far from the only disease of its kind. Measles, for example, is known to be able to last in the air for up to two hours. Tuberculosis, although a bacterium, can to remain in the air for six hours.
Evidence of the aerial spread of Covid-19 however, as the microbiologist says, already seems to be a lot.
Several great studies indicate, among the main ways of spread, the fact that the coronavirus remains in the air. Other studies have suggested that the virus may remain in aerosolized droplets for hours.
Finally, the new study conducted by Roy and his team in Tulane shows that SARS-CoV-2 infectious aerosolized particles they could actually linger in the air for up to 16 hours and maintain infectivity much longer than MERS and SARS-CoV-1.
We still don't know what gives SARS-CoV-2 this "air advantage." But that may be one reason why this is a pandemic, and not simply a small outbreak like any other coronavirus.
If the coronavirus is in the air, how do you stay safe?
Whether the virus is airborne is not just a scientific question. First of all, it would mean that in places where the virus has not been adequately contained (for example, the USA), the economy must be reopened more slowly, under stricter regulations with more careful health practices.
It would mean that our current tactics to stop the spread are not enough.
Roy he would like to see much more rigor on the use of masks outside the home. “This virus spreads rapidly,” she says. “And the mask can do a lot to interrupt its transmission. I think anything that can stop the production of aerosols in the environment is helpful.”
With all the limits of the case
We know that although masks can limit the spread of larger particles, they are less useful for smaller ones, especially if they are not worn well.
“I would like us to stop relying on the idea that masks will solve everything and flatten the infection curve,” says the microbiologist. “It's magical thinking. It will not happen." For masks to really make a difference, they should be worn at all times, even within the family. And it is almost unthinkable, certainly impossible.
All the evidence from many, many studies however tends towards the conclusion that airborne transmission is “the primary and perhaps most important mode of transmission for SARS-CoV-2”.
In that case the time and effort dedicated to sanitizing every single surface over and over again was a great waste of time. “We don't have to worry so much about cleaning every single surface we touch. The focus should be on other factors, such as where we spend our time,” says Roy.
Crowded spaces
One of the biggest questions we still have about Covid-19 is how much viral load is needed to cause infection.
If the coronavirus is in the air the answer changes: the smaller particles will not carry as large a viral load as the larger ones, but since they can linger in the air much longer, it may not matter: they will accumulate in larger concentrations and they will distribute more widely and for longer.
The more people entering and exiting an indoor space, the more likely it is that someone infected will show up. The longer infected individuals spend in that space, the higher the concentration of virus in the air over time.
This is particularly bad news for the spaces where people gather for hours and hours, such as restaurants, bars, offices, classrooms and churches.
Airborne transmission doesn't necessarily mean these places need to stay closed (although that would be ideal): but cleaning the surfaces with a disinfectant and having everyone wear masks will not be enough.
To reopen safely, these locations will not only need to reduce the number of people allowed inside at any given time, they will also have to reduce the time people spend there.
Ventilation should also be a higher priority. This will be a big deal for older buildings which usually have worse ventilation systems, and areas with many of these may need to remain closed for much longer.
The impact of asymptomatic spread (transmission by people who don't feel sick) and superscoverers further compounds the problem. But (here, finally, is some good news) one Research conducted by the United States Department of National Security showed that in the presence of UV light, aerosolized particles of the size studied by Tulane researchers they would disappear in less than a minute.
Well, then, i robot with UV located in hospitals, shopping malls, shops and stations to sanitize environments.
For many places, the damage of the economic closure could be too high a price to keep the virus in check. The best strategy would be to behave as in the early lockdown periods. It's possible? It's impossible?
The constants, in any case, must always be the same, if you want to contrast the aerial spread of Covid-19.
