WHO (World Health Organization) had earlier denied that coronavirus is airborne. Take a look at this.
After researchers worldwide studied the transmission and prepared an evidence-based report, WHO accepts that coronavirus is airborne, indeed. But the damage is already done, and fatalities are increasing.
You can read it here: WHO acknowledges ’emerging evidence’ that coronavirus is airborne.
Watch on YouTube – WHO accepts that coronavirus is airborne.
Coronavirus is Airborne. What now?
Now that many countries have mandated the use of masks in public. For example – Austria, the Czech Republic, Slovakia, and others will follow suit. We need to understand what we can expect from these masks. We need to understand how airborne transmission occurs. Different diseases have different modes of transmission. The airborne transmission happens via small particles, by contact, or fomites, fecal-oral transmission, and many more.
One disease can have multiple modes of transmission. However, bacterial and viral infections have more than one mode of transmission and they are called Anisotropic. Disease severity can differ for a given disease depending upon the mode of transmission. Influenza, transmitted by aerosols is thought to be associated with a severe illness than influenza that’s transmitted via contact or fomites.
We’ve heard that airborne particles smaller than 10 micrometers have the potential to penetrate below the glottis. And particles smaller than 5 microns can penetrate further down into the alveolar space. Now imagine this, particles that penetrate deeper into the lungs cause pneumonia; whereas, particles that penetrate into the upper respiratory tract cause upper respiratory tract infections like bronchitis.
And as we all know, pneumonia is a much more severe as well as debilitating disease. Severely affected symptomatic patients with COVID-19 (Coronavirus Disease 2019) tend to have pneumonia rather than upper respiratory tract disease. This indicates that the virus penetrates deep down into the lungs by tiny airborne particles. So the lower the particle size, the more problematic.
How are these droplets and aerosols actually produced?
Coughing, sneezing, spitting, probably even through regular breathing or just speaking produces these droplets. Now you would think that someone with COVID-19 or influenza for that matter would infect someone by coughing up virus-containing particles that would then infect others?
Does coughing infect others?
Yes, but it’s not that simple. When someone coughs or sneezes, that cough or sneeze usually produces particles of larger size. And these particles contain less virus than small particles and are less likely to penetrate into the lungs. The small particles carry the potential to penetrate into the lungs. If they carry the virus, it infects the other person.
According to this intriguing paper published by Donald Milton at the University of Maryland, “Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community”
They collected exhaled breath of patients with influenza for 30 minutes; the participants face was inside of a large open end of a cone-shaped device.
The inlet cone draws in 130 liters of air per minute and allowed participants to talk, cough, breathe, and sneeze naturally for the full sample collection duration.
They requested the test subjects to breathe normally and to recite the alphabet once at 5, 15, and 25 minutes. Also, they collected coarse or large particles of greater than 5 microns and fine or small particles of below 5 microns in diameter.
They counted audible, spontaneous coughs and sneezes during the breath collection by direct observation in real-time.
Here’s what they found. Look at this image carefully.
On the left side the concentration of viral RNA and course aerosol and on the right fine aerosol.
They are stratified according to the cough frequency. They compared those who never coughed to those who seldom coughed – just once or less per minute, to those who coughed frequently, i.e. more than once per minute.
Now, one would expect that people who cough frequently would produce more coarse particles and that these coarse particles then contain more viruses.
Value Read: How the sugar industry shifted the blame on fat.
That’s not what they discovered. They found that viral particles contained within the coarse particles showed similarity when frequent coughers were compared to infrequent coughers. The RNA that comes in contact within coarse particles of infrequent coughers and frequent coughers are very similar and not significantly different.
Wikipedia on Coronavirus here.
Important finding on airborne transmission
They found that viral RNA contained in fine particles dramatically increased in those who coughed frequently compared to those who coughed infrequently or those who never coughed.
So what this means is that a person produces particles with high viral load, not when they cough, but actually during times when they don’t cough.
These observations help in concluding that cough is in part, an epiphenomenon, and more of a response to irritation in association with high viral loads in distal airways, rather than being a direct source of infectious aerosols.
So cough and fine virus-laden aerosol particles are associated, but not causally.
What is the proposed mechanism of fine aerosol production?
Many researchers have proved that periodic generation of exhaled aerosol particles from healthy lungs via small airway closure and reopening. It’s hypothesized that respiratory infections period, closing & reopening airway frequency increases. This is due to inflammation with increased aerosol generation and contagiousness.
This suggests that individuals who are sick produce fine virus-laden particles during speaking and breathing that have a high viral load and can travel far down into the lungs of a susceptible individual.
And these are the particles that go unfiltered well by a surgical mask.
Julian Tang and co-workers have created a visualization of breaths exchanged by two people in conversation, standing one meter apart.
Most of the time, air-puff they let out remain separate, but portions of their explanations do sneak from each person breathing space into the others. It proved that anything less than 2 meters is like exposing yourself to the virus if the other person is a carrier.
The above post explains how the coronavirus is airborne.
So, it’s possible that in crowded public transport or public events, where people can breathe on each other, may also lead to transmission of infection, even without any coughing going on.
This is so important and shows why social distancing, staying at least two meters away is so important even if you should be carrying a mask.
On a related note, keep yourself healthy and maintain a safe distance. Let us know your thoughts in the comments.