Most countries are ignoring aerosols, a significant route of COVID-19 infection

There is controversy over how Sars-Cov-2 spreads from human to human.  China and South Korea believe that a significant route of infection is through aerosols; they are trying to safeguard against it as much as possible.  The World Health Organization argues that the coronavirus is NOT spread through aerosols.  Those who follow the WHO’s line of thinking generally do not take precautions against aerosols (unless there is an aerosol-generating procedure in the hospital).

As investors, we need to pay attention to these differences of opinion.  Countries acting on bad advice may take far longer to contain COVID-19 in their country.

Droplets and aerosols- what are they?

The moisture in your breath is made up of droplets and aerosols.  Droplets simply refers to larger droplets of water mixed with the other things in your saliva (e.g. salt, proteins, viruses, bacteria, etc.).  For example, if you spit, there are very large droplets of water coming out of your mouth.  When you breathe, sing, and eat, there are also very tiny droplets of water coming out of your mouth.  Those droplets are so small that you cannot see them.  But they exist.

You can think of a spray bottle.  If you look closely enough, you can see that there are larger droplets and tinier droplets.  There is a continuum of droplets from very large to very small.

Human beings exhale both droplets and aerosols.  As mentioned previously, it’s a continuum of sizes from large to small.  Because humans produce both droplets and aerosols, it is very difficult for epidemiologists to figure out if somebody has been infected from droplets or aerosols.

How far do aerosols travel?

Imagine somebody smoking.  Those standing close to the smoker will be exposed to a very high concentration of smoke.  They can smell it.  But you can also see that the smoke can travel pretty far on a windy day.  As the smoke travels further away, it gets diluted with air.  Those standing further away from a smoker will have a hard time smelling the smoke.

What we do know is that aerosols travel pretty far, and that concentration drops significantly when people are far away.

I would be highly skeptical about people who claim that infection is through droplets but not aerosols.  It is difficult to scientifically prove that infection spreads through droplets but not aerosols.  Because the concentration of aerosols drops off rapidly with distance, they can produce data that looks like the droplet theory is true.  We need high-quality studies to answer the scientific question but those studies don’t exist right now.  We don’t even fully understand how influenza is spread because the science is not there yet.

What American scientists are saying

There are some American professors who study aerosols who also take the aerosol theory very seriously.  See the links at the end of this article.

Evidence that infection spreads through aerosols

  • Case reports:  We have observed that some people have become infected even though they were not in close contact with the infected individual.  They were infected even though it is highly unlikely that they were in contact with droplets from the infected individual.  This was the first evidence that coronavirus spreads through aerosols.
  • Genetic material from coronavirus is found in aerosols.  There are multiple papers on this now, linked to at the end of this blog post.  Researchers haven’t yet taken the additional step of culturing the virus and providing evidence that the virus found in air is actually alive.
  • Aerosols would explain “super spreaders”:  There have been a few events where a single person infects tens of other people all at once.  This should not be possible under droplet theory because droplets do not travel that far and it is highly unlikely that the infected individual spread droplets everywhere.  Aerosols would provide a better explanation as it explains how somebody was able to infect others without standing close to them.
    An additional theory is that singing generates more aerosols than normal breathing.  The super spreading events at a Korean church/cult and in an American choir practice are relevant to this theory.
  • Aerosols would explain why protective gear works most of the time but not all of the time.  Many different theories explain why healthcare workers become infected despite trying to avoid infection, and why they become infected at low rates despite close contact to infected patients.  Aerosol theory is one of those theories.

You should be careful because most scientific theories turn out to be false once they are actually tested.  It could very well be the case that coronavirus spreads through some other mechanism.  For example, some people believe that droplets land on the ground, dry up, and turn into an aerosol once wind/air blows on it.

Another theory is that coronavirus spreads through droplets and contact (fomites).  A droplet falls onto the handrail in a staircase.  Somebody touches that handrail and then touches his/her face and then the virus somehow travels to the respiratory tract, ultimately leading to infection.  People who advocate for droplet theory (and against the aerosol theory) will generally argue that droplets and contact/fomites are the routes of transmission for Sars-Cov-2.

On a practical level, we should assume that the virus spreads through droplets, aerosols, and fomites.  This is what China and South Korea does.

Precautions against aerosols

Watch out for HVAC.  When China quarantines travellers, it tells quarantined individuals not to use the air conditioning.  In many buildings, the HVAC system is designed to recycle air throughout the building to conserve energy.  Many countries aren’t paying attention to this at the moment.

Ask/force infected patients to wear masks.  This helps to contain aerosols in the hospital or in home quarantine.  Many countries aren’t paying attention to this at the moment.  Hong Kong makes its patients wear masks so that they are less infectious and are less likely to be infected.

N95 respirators work better than other masks which do not filter as much aerosols.  However, these masks do let some aerosols through.  They reduce but do not completely eliminate the possibility of becoming infected.  If the best masks are not available, then the weaker masks are better than no mask at all.

Protective coverings for most of the body?  Some people believe that aerosols can land on the body and turn into an aerosol again.  One way to minimize the risk of infection from this route is to wear protective gear over most of the body.

Distancing.  The simplest way to think of this is to imagine somebody smoking.  Wind and distance affect exposure to smoke.  Social distancing reduces exposure.  Larger distances will reduce exposure even more.

Eye protection? (e.g. goggles)  Aerosols can land on the eye.  Or, if you believe in contact/fomites as a means of transmission, the virus may end up in the eye by somebody rubbing their eyes.  I actually don’t understand why Western healthcare workers don’t wear goggles.  We need to take both fomites and aerosols seriously.

If coronavirus can be spread through aerosols, then the lack of protection gear in the US is a huge issue

If the aerosol theory is true, then medical workers should be wearing high levels of protection.  Ideally, they should have a N95 respirator (which doctors in the US are running out of).  Healthcare workers in China and South Korea tend to wear a lot more protective gear than North American healthcare workers.

In a NBC video, staff at a Korean drive-thru clinic are shown wearing eye protection, a N95 respirator (3M 9210), and a face shield.

Other drive-thrus have workers without the face shield.

Compare that to this Canadian healthcare worker who is not wearing eye protection (he is wearing a face shield though) and is wearing a surgical mask instead of a N95 respirator.

Source: CBC article.

In China’s airports, regular airport workers wear high levels of protective gear with most of their body covered.  John Hempton’s blog has a link to this video:

You can see the hotel workers wearing substantial protective gear at the 2:22 mark.

Protection for citizens

If coronavirus is spread through aerosols, then citizens should definitely be wearing a mask.  Any mask is better than nothing.  However, health officials may not want to admit that they screwed up in telling citizens not to buy masks.

I would however point out that the Chinese government is not forcing its citizens to wear masks in public.  While the CCP continues to take extraordinary measures, it has not implemented this low-cost measure.  This may be for political reasons.  The propaganda story that the Chinese government tells its citizens is that it has done a wonderful job in protecting them against the coronavirus and that they can go back to living their normal daily lives.  Meanwhile, at Chinese airports, life is definitely not normal.  There are heavy travel restrictions and non-healthcare workers have been instructed to wear very high levels of protection.

In general, it may be very difficult to stop the spread of coronavirus

In my previous blog post, I talked about the false negatives from the RT-PCR test.  Because the tests are unreliable, it’s hard to figure out if the uninfected truly are uninfected.  This can make contact tracing much less effective when you aren’t contact tracing a third of the infected.

So, China is meticulous.  Instead of making dumb assumptions about test results, they act as if high-risk individuals with negative test results are infected.  They force travellers to China into a strong quarantine (not the home isolation stuff that South Korea does) despite negative test results.

This may help you understand why China and South Korea are putting so many restrictions on travel despite containing the virus in their country.  It is very difficult to stop its transmission.

You can contrast their paranoia to the practices in most developed countries.  Currently for contact tracing, there are a lot of Western health officials who believe that you only need to quarantine individuals who have been in extended contact with an infected individual.  If a person was near an infected person for only 15 seconds, then health officials may not necessarily force them into quarantine (especially if their PCR test result is negative).

Another major concern is that Western societies operate under the illusion that medical tests are near-perfect.  If an everyday citizen receives a negative PCR test result, they will automatically assume that they aren’t infected and they will act as if they aren’t infected.  It’s socially acceptable to go to work if you have the flu or the common cold.  So, these people will do things that they should not be doing.

The market may be missing something

Right now, there are a lot of people who believe that:

  • Healthcare in developed countries is high quality.
  • We can simply go “full Wuhan” on the virus to end it.  If we simply copy China and its “draconian” methods, containing the virus will be easy.

I am scared because we have cultural and political obstacles to overcome.  There are a range of outcomes.  We could listen to Chinese medical experts and do what China did.  In theory, copying China should not be hard.  But in practice, there are Western medical “experts” who are very much against this.  They may fight hard to defend their medical dogma.  Other honest and intelligent people will likely side with the medical “experts” at the CDC and the WHO to stay consistent with their past behaviour.  They are well aware that there is a lot of discrimination against non-scientific individuals who peddle woo and pseudoscience.  If anybody stands up to the “science” establishment, then that person will face discrimination.  Human beings do not want to end up on the wrong side of a lynch mob so there will be a lot of people who will side with the Western world’s “science” establishment.

Be prepared for uncertainty because containing COVID-19 may not be as easy as most people think.


*Disclosure:  Here’s my current bias: I am more long the stock market than I am short.  I am shorting airlines even though I don’t understand the airline industry well; it may be a bad short.

Medical Twitter

There are American science professors on Twitter who take the aerosol theory seriously:



News articles

Choir super spreader event – This news article is a good summary of a super spreader event and the science surrounding it.

COVID-19 Travels in the Air Study Says – This sort of summarizes Linsey Marr’s opinion.

Academic papers

Transmission Potential of SARS-CoV-2 in Viral Shedding Observed at the University of Nebraska Medical Center – COVID-19 patients produce aerosol particles.

Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 – The virus is stable in aerosols.

Air, Surface Environmental, and Personal Protective Equipment Contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) From a Symptomatic Patient – The virus was found in an air exhaust vent, suggesting that the virus travels in aerosols.

Turbulent Gas Clouds and Respiratory Pathogen Emissions – Aerosols can travel long distances.


The WHO argues that the COVID-19 virus isn’t spread through aerosols.


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