Background
According to WHO, the virus is mainly spread during close contact which is defined as one (1) meter or 3 feet while the CDC defines it as two (2) meters or 6 feet.
A new updated study pushes this distance to four (4) meters or 13 feet.
They are also spread through small droplets or respiratory droplets. Droplets are defined as particles that consist mostly of water which is large enough to fall to the ground upon produced. It’s made through the process of coughing, sneezing and talking.
They may also be produced by breathing. However, contrary to aerosols, they rapidly fall to the ground and surfaces and don’t generally spread through the air over large distances.
Upon dropping to the ground or any surface, the virus may be able to survive for 72 hours (three days).
According to a new study from the National Institutes of Health, CDC, UCLA and Princeton University in The New England Journal of Medicine, the virus is detectable in aerosols for up to three (3) hours, copper up to four (4) hours, cardboard up to 24 hours or one day, and up to two or three days in plastic and stainless steel.
An interesting look at respiratory / microdroplet spread can be seen by an experiment performed by NHK Japan. It suggests that microdroplets emitted while sneezing and coughing and during conversations stay in the air for longer than normal droplets, potentially posing a uniquely dangerous risk for coronavirus infection.
The Airborne Debate
Let us define first what is airborne spread and droplet spread – the latter is proven to be how Sars Cov 2 travels.
Airborne spread means that a certain pathogen can be carried up to the air and spread to long distances and still be viable enough to cause an infection.
This is usually through aerosols – defined as liquid or solid particles suspended in air. While it’s proven that some coronaviruses spread through this process, the coronavirus causing COVID-19 has not been proven to spread in this manner.
However while the virus was detected in aerosols for up to three hours in the studies mentioned, there has yet to be evidence that contracting these particles are enough to cause infection because there needs to be enough viral load.
One difference that airborne spread has with droplet spread is size. Particles that contribute to the formation of aerosols ultimately have a size less than 5 μm. Which permits it to be light enough to be carried through the air, while droplets have sizes more than 5 μm, making it fall to the ground after it is created, the heavier the particle, the faster it falls.
Examples of infectious diseases with airborne transmission include: Measles, Chicken Pox, tuberculosis and influenza.
Examples of infectious diseases with droplet transmission include: measles and influenza as well, the Rhinovirus which is generally what causes our common cold, and of course Sars Cov, Sars Cov 2 and coronaviruses in general. Again, its true that some coronaviruses may spread through airborne transmission but Sars Cov 2 specifically has not been proven to spread through this method, and additionally while Sars Cov 2 is indeed detected on aerosols (for a few hours), there is still not enough evidence that these aerosolized particles carry enough viral load to cause an infection.
To make an estimated contrast — put 20 people inside a large room. With the same timeframe and circumstances, a person with measles may be able to spread the virus to everyone in the room because it is airborne, while a person with COVID 19 will infect 3, 4 maybe up to 6, and most likely those who are closer.
Airborne with Conditions
Thing is, there’s currently a huge debate on the medical and science community regarding the transmission of COVID-19 through the air.
Based on research on other respiratory viruses, experts originally stated that aerosolized SARS-CoV-2 likely isn’t the primary driver of transmission in “everyday settings,” but could pose a danger in health care settings where specialized equipment is used.
According to WHO airborne transmission may be possible in specific circumstances and settings in which procedures or support treatments that generate aerosols are performed i.e., endotracheal intubation, bronchoscopy, open suctioning, administration of nebulized treatment, manual ventilation before intubation, turning the patient to the prone position, disconnecting the patient from the ventilator, non-invasive positive-pressure ventilation, tracheostomy, and cardiopulmonary resuscitation.
However, a recent account of members in a large choir group who tested positive for COVID-19 after rehearsal raises the possibility that aerosols may drive transmission beyond the bounds of a hospital.
While various experts who studied samples taken from the air in various places most especially the hospital setting where COVID-19 patients reside found viral RNA, there is still no data indicative that they are viable enough to cause infection.
To avoid confusion, while the virus infused microdroplets floating around in the room may get to you in a span of hours, there is a certain amount that your body may need to contract before getting the infection – hence the statement “not enough viral load” since some or most, if not all, of the droplets eventually fall to the ground or any surface, in contrast to a truly airborne virus which ultimately stays in the air for longer, in this same span of hours you are more likely to contract enough viral load to be infected – This is of course if the two scenarios have the same circumstances, because if you like to be intimate with every inch of the room then you won’t only get Sars Cov 2 but a myriad of other diseases.
Social Distancing
The reason why strict social or physical distancing measures are implemented, though the virus is not proven to spread through airborne means, is because respiratory droplets should not be taken lightly.
While it’s true that droplets eventually fall to the ground, the virus may still be able to come in contact with a person proximal to an infected (less than 13 feet per new evidences by the CDC) through breathing and remain in the air for a few hours – while there is little to no evidence that suggests that this already causes infection for a reason that a certain amount of viral load is needed, it is still paramount that necessary precautions are done as enough viral load may cluster if this method of contacting viral particles is frequent i.e. In the hospital setting.
In conclusion, current evidences still point that COVID 19 is spread through respiratory droplets and not aerosols and is therefore not airborne. The virus may be viable in surfaces for up to 3 – 4 days, and contact with such surfaces may lead to infection.
The virus may be detected in air in enclosed spaces most especially the hospital setting in which procedures that produce aerosols happen ie. intubation – and may stay up in the air for three hours, but not enough evidence has suggested that these “floating components” are viable enough to infect an individual, thus experts are unable to conclude that COVID-19 may be transmitted through airborne means, yet, but this does not mean we have to become complacent.
REFERENCE:
- New Evidence that Virus travels as far as 13 feet
- New coronavirus stable for Hours on surfaces, March 17, 2020
- A choir decided to rehearse March 29, 2020
- Is the coronavirus airborne? Experts can’t agree, April 2, 2020
- Coronavirus Spread by Talking and Breathing, April 6, 2020
