Medical Science, Medical Ethics, COVID-19

The article goes on to say:“We are not convinced that aerosols are the only pathway,” she said.So the WHO is not convinced that aerosols are the primary COVID-19 communication vector.
  • #1


Science Advisor
Homework Helper
TL;DR Summary
WHO is balking on pointing its finger at COVID-19 aerosol.
Medical science constrained by "Do no harm".
There is a COVID-19 issue that has been brewing for at least a couple of months: Is the primary COVID-19 communication vector aerosols?
But only in the past couple of weeks has this issue started to come to a boil - as in this article:

The difference here is aerosol vs. droplets; colloidal dispersion vs. mist.
Both are emitted when you sneeze, sing, or talk. But droplets drop to the floor in minutes.
A colloidal dispersion, in contrast, does not.
If you really hate cigarettes, then cigarette smoke makes for a good model. When talking with someone who is smoking, you would like to keep your distance - and six feet isn't too bad. But if you're indoors, it's not going to matter. The smoke will build up and within half an hour, it will be time to leave or suffer.
The COVID-19 virus is about 125 microns in diameter - perhaps double that if you include other matter hanging on to it. That would make it as bad as cigarette smoke in terms of persistence. It would hang in the air for hours (and long after the smoker had left) - but only if the air was still. Moving air could keep it airborne indefinitely.

So, in an indoor COVID-19 setting, the difference between aerosol and mist is hugely significant. If COVID-19 can be communicated by aerosol, then a whole new set of rules related to ventilation would need to be researched and developed and COVID-19 contagion models would need to be revised.

So, does COVID-19 efficiently communicate through aerosols?
1) The Skagit County Choir: This is a well-publicized event that took place in March. The CDC report is here (warning, slow link, be patient):
CDC Report on Skagit County "Super Spread" event.
They don't really provide a "synopsis", but under the heading "What is added by this report", they say:
Following a 2.5-hour choir practice attended by 61 persons, including a symptomatic index patient, 32 confirmed and 20 probable secondary COVID-19 cases occurred (attack rate = 53.3% to 86.7%); three patients were hospitalized, and two died. Transmission was likely facilitated by close proximity (within 6 feet) during practice and augmented by the act of singing.
This report cites the 6-foot rule several times and it mentions both droplets and aerosols. But the case against droplets is not as strong as this report suggests. For example:
First, the seating chart was not reported because of concerns about patient privacy. However, with attack rates of 53.3% and 86.7% among confirmed and all cases, respectively, and one hour of the practice occurring outside of the seating arrangement, the seating chart does not add substantive additional information.
This suggests that seating proximity to the index patient was not well-correlated to the contagion - at least not positively correlated.

2) What we exhale: This has been well-examined by Sima Asadi, et al - Asadi Study - What we exhale.
It has long been recognized that particles expelled during human expiratory events, such as sneezing, coughing, talking, and breathing, serve as vehicles for respiratory pathogen transmission. The relative contribution of each expiratory activity in transmitting infectious microorganisms, however, remains unclear. Much previous research has focused on coughing and sneezing activities that yield relatively large droplets (approximately 50 μm or larger) easily visible to the naked eye. Less noticeable, but arguably more infectious for some diseases, are the smaller particles emitted during sneezing and coughing as well as during breathing and talking. These small particles are believed to be generated during breathing and talking from the mucosal layers coating the respiratory tract via a combination of a “fluid-film burst” mechanism within the bronchioles and from vocal folds adduction and vibration within the larynx. The particles emitted during breathing and typical speech predominantly average only 1 μm in diameter and are thus too small to see without specialized equipment; most people outside of the community of bioaerosol researchers are less aware of them.
This article also suggests that aerosol particles may be more infectious that droplets.
One interesting phenomena explored in this study is the "super-emitter", people who emit an order of magnitude more particles than average. What I have not seen in any study is evidence of a super-emitter being tied to a super-spreader event. Quite the opposite: There is commonly a caveat saying that (in the context of disease-containment practicality) it is not possible to diagnose someone as a superspreader. My point is that I see no reason to conclude that superspreader events are most commonly "sponsored" by super-emitters.

So why is the WHO balking?
For the same reason I did not post this weeks ago. There is little more than (excuse the pun) a smoking gun.
From the NY Times (NYT Article on Open Letter to WHO):
Dr. Benedetta Allegranzi, the W.H.O.’s technical lead on infection control, said the evidence for the virus spreading by air was unconvincing.

“Especially in the last couple of months, we have been stating several times that we consider airborne transmission as possible but certainly not supported by solid or even clear evidence,” she said. “There is a strong debate on this.”

Which brings us directly to the issue of ethics. You can't actually recreate a super-spreader event in the lab. It would be unethical. As a doctor or a scientist, it is unethical to send people (even enthusiastic, well-informed volunteers) into harm's way for the greater good. But for elected executive office leaders, it is standard practice. Bear this in mind the next time you see your favorite national executive speaking in contrast to your favorite national medical advisor. They are speaking from separate roles.

Here is one more article which bears on how profound the difference would be between aerosol and droplets - although that is not the gist of the article:
MIT Superspreader Article June 15
What’s the impact of superspreaders for covid-19? Researchers are beginning to come to a consensus after several new studies showing that Coronavirus transmission more or less follows the 80/20 Pareto Principle (named after Italian economist Vilfredo Pareto): 80% of all consequences come from just 20% of the possible causes. For covid-19, this means 80% of new transmissions are caused by fewer than 20% of the carriers—the vast majority of people infect very few others or none at all, and it’s a select minority of individuals who are aggressively spreading the virus. A recent preprint looking at transmission in Hong Kong supports those figures, while another looking at transmission in Shenzhen, China, pegs the numbers closer to 80/10.
What that article is really discussing is "super-spreader" events - not specifically super-spreaders.
But cutting the infection rate by a factor of 5 (an 80% reduction) would stop Covid-19 almost immediately.
  • Like
Likes atyy
Biology news on
  • #2
The open letter to the WHO has now been published. A link to the PDF is at this URL:
Open Letter to WHO
  • Informative
Likes Tom.G
  • #3
.Scott said:
The COVID-19 virus is about 125 microns in diameter -
I think you mean that the COVID-19 virus itself is about 125 nanometers in diameter. 1000 times smaller in diameter and 1 billion times smaller in volume than what you said.
  • Like
Likes hutchphd
  • #4
"As a doctor or a scientist, it is unethical to send people (even enthusiastic, well-informed volunteers) into harm's way for the greater good. "

So was it unethical to send me to Vietnam for two years or send someone to a more popular war? I like many vets would gladly give my life for the greater good in the "war" with Covid-19.

More than one hundred thirty thousand of our countrymen have died. How could it be considered unethical for a few more "well-informed volunteers" to fight this battle?

As I look out my window on the 4th of July and see 40 people having a party in Miami Florida, getting drunk and no mask to be seen I wonder if I have lost my mind wanting to protect you. I am compelled to try...even when you have no regard for your own safety or anyone else.

Best regards,

  • #5
Evidence is being found that Covid infections are producing long term damage to various organs (lung, liver, kidney, heart, and brain). Also, there is some concern that there may not be a permanent immunity. Will this mean that the reinfection of the population will result in a larger mortality rate compared to the initial infection? If the virus retains its basic characteristics (organ damage) and mutates periodically like the flu could this lead to a higher mortality rate if we do not very aggressively protect ourselves? It really sounds like you do not want to get this a second time.

Do those with no, minimal symptoms or not requiring hospitalization suffer significant but unrecognized organ damage? Should recovered people have routine diagnostic tests to assess the possibly affected organ damage? What about the possibility of latent effects? This virus seems to be doing things that its relatives do not.

This virus has left a lot to be investigated.
  • #6
I hear lots of concern that there may be limited immunity, but I have heard no reports of anyone getting it twice. Is anyone aware of any cases where someone has gotten it twice? The first major cases were in January/February. If the immunity were really short term, there should already be people being re-infected.
  • #7
phyzguy said:
t I have heard no reports of anyone getting it twice. Is anyone aware of any cases where someone has gotten it twice?

We have a forum member who says he got it three times.
  • #8
FWIW- I cannot find any clinical case studies that show Covid reinfection -- using google scholar. Which proves nothing of course. Except maybe that no physician has reported it if it does occur.

There are many case studies of Covid with secondary and post-infection serious problems. This pathlogical nastiness is also reported with measles, MERS, chicken pox, etc.

It is possible that our above example reinfection is really prolonged disease process. Or maybe something more psychological.
  • Like
Likes Evo
  • #9
Referencing above post about reinfection leads to duration of immunity.

Screenshot_2020-07-11 Coronavirus Pandemic Update 93 Antibodies, Immunity, Prevalence of COVID...png

Which finds 40% of asymptomatic patients who were seropositive , when tested later (IgG) were found to be seronegative. So this appears to imply the possibility of asymptomatic patients as sources for reinfection.

It may also suggest that there is a possibility of limited persisting resistance from vaccination.
  • #10
If a person has a reoccurrence of symptoms is that a result of a reinfection or a relapse from the initial infection.
This is just one article but some scientists believe that even after symptoms disappear a relapse could occur for COVID. My OP presupposed a somewhat longer immune period such that a second wave might be that which poses a risk to those who have lost their immunity. I would suppose a relapse has a shorter time for symptom reoccurrence compared to if there is a temporary immunity.
  • #11
I'm actually a bit surprised that the idea of aerosol spread caused so much discussion its basically a debate about droplet size which in nature have no clear cut off point and people generate the full range of sizes all the time. Singing and talking loudly seem to be a particular problem, which is why bars are considered such a problem, and religious services of course. I think over time its become increasingly clear that infection rates are clearly associated with the viral dose, the length of exposure and being in enclosed environments. While detection of viral particles in the air isn't a good indicator of infectivity the circumstantial evidence has become overwhelming. In fact several countries had altered their guidelines before WHO got its act together.

Its a bit inevitable that we appear to be playing catchup all the time, we don't know enough about this infection but the idea of air born spread is providing a rational for the increased infection rate in the warmest states in the US. People stay indoors to avoid the heat, its also starting to inform the predictions of a second wave in winter, when cold weather causes the same behaviour.
  • #12
Planobilly said:
"As a doctor or a scientist, it is unethical to send people (even enthusiastic, well-informed volunteers) into harm's way for the greater good. "

So was it unethical to send me to Vietnam for two years or send someone to a more popular war? I like many vets would gladly give my life for the greater good in the "war" with Covid-19.
You may have misinterpreted my statement. I was not saying that I was a doctor or a scientist. I was describing an aspect of the role of doctor or scientists. So it would have been unethical for someone acting as a doctor or a scientists to send you to Vietnam. But entirely ethical (but perhaps not well-advised) for a POTUS to send you there.
  • #13
A research team at the University of Florida has successfully infected cells with the COVID-19 virus from an airborne aerosol generated from a COVID-19 patient.
Their work is prepublished in medRxiv: Covid-19 Aerosol Experiment

This story has been carried by the New York Times.
  • #14
I guess we here on this forum are generally most interested in the understanding of the technical details of the virus. Being in my seventies and with some adverse health conditions, how all this works is pretty important to me.

I own an agribusiness so I have several hazmat conditions to deal with in normal times. Protecting myself from airborne chemicals is pretty well known and not too different from pathogens . I am not sure I understand why the general public in many cases are so opposed to using protective gear. While it is all together necessary to do the research to understand in detail how this virus is communicated, the technology to stop the communication of the virus is well known.

Science is very interesting to me in general but for me the application of the knowledge is the most important aspect. There is no way to predetermine if a medical solution in what ever form will ever be developed. I think there will be a solution and I hope I am correct in that assumption.

Currently there seems to be a good bit of speculation and not enough hard facts in all these reports being discussed. We defiantly need to build a better well funded system to address these issues. What is truly
unethical is the fact we don't have such a system. It is a pretty forgone conclusion that this is not the last pandemic we will face.

What really bothers me is the disregard by to many people in government and the public of science in general.
If you think professionals don't know what they are doing, you go fly the aircraft next time you need to
  • #15
From the newly revised CDC guidelines:
Some infections can be spread by exposure to virus in small droplets and particles that can linger in the air for minutes to hours. These viruses may be able to infect people who are further than 6 feet away from the person who is infected or after that person has left the space.

I would also note that when the virus is communicated this way, it has the potential to seat itself much deeper into the respiratory tract than with larger droplets or fomites.
  • #16
Thanks for share this review. I also heard medical cannabis can help with COVID.
  • #17
carlopinini said:
Thanks for share this review. I also heard medical cannabis can help with COVID.
It would be unusual and seem counterintuitive to treat breathing problems with smoke. Do you have any reliable references for that?
  • #18
I meant CBD oil. No, I haven't references.
  • #19
  • #20
Its natural that when faced with an uncertain threat people will search for some sort of certainty and sometimes even when we have more precise details this really doesn't translate into anything useful, in biology this is not unusual in fact it is more often predictable. Understanding an infectious disease is not simply a matter of exposure, though that's a necessary condition, its just that there are so many other variables to consider. It is clear that the virus can remain air born and viable for quite some time, it may also be widely disseminated but these things are poor predictors of risk.

Even the current suggestions on reducing risk are presented in a way to suggest precision, this precision is achieved by selectively ignoring many of the factors involved, they are gross generalisations, they have to be, to be useful. The lancet article discusses some of the advice but for most people the take home message is that the distance from the source is important, the further away the better really and masks can help. The trouble is that the relative importance varies depending on other risk factors, the case of the Skagit choir simply shows that prolonged exposure to high levels of the virus in an enclosed space changed the risk equation.

There are similar issues in understanding super spreading events, there are no super spreaders, as people, viral shedding is really a function of the stage in the disease process, its the environment that the person is in that controls the infection risk.

The issue of reinfection brings with it similar problems, its not that it occurs, it would be a very unusual disease indeed if it didn't, the real interest is in the rate of reinfection, its features and trying to understand the underlying processes involved. It does seem that reinfection isn't common and when it does occur, its usually as a mild or asymptomatic illness, this is what we would expect. However in some people the disease can return in a more sever form and the more detail we get about this virus the more complex this issue becomes. In studies that looked at cross immunity with other coronaviruses around 40 different cross reactive antibodies were identified, however the majority of these that targeted the virus envelope were neither protective or able to modify the infection. Only the antibodies that targeted the spike proteins were really effective and its already clear that people antibody responses vary. We also know that the virus itself has a direct effect on our immune system, possibly linked to genetic differences, and can damage lymphocytes. There is some interesting stuff linking Neanderthal genes to susceptibility currently around.

The reassuring thing is that it seems the vaccines will avoid these problems and produce a strong more predictable effect. Unfortunately the new FDA guidelines introduced really, to reassure the public, will actually delay any vaccine approval in the USA for at least two months, this could have serious consequences.
  • #22
carlopinini said:
Thanks for share this information. I found article about only cbd oil.
Unfortunately this is simply an advert, this appears to be true for most of the links making this claim. I think the claims are loosely based on the fact that cbd does have effects on the immune system. I did find a discussion document on what is at least a credible site and it does have reference links.
  • Like
Likes BillTre

1. What is the current understanding of COVID-19 and how is it spread?

COVID-19 is a respiratory illness caused by the novel coronavirus SARS-CoV-2. It is primarily spread through respiratory droplets when an infected person talks, coughs, or sneezes. It can also be spread through contact with contaminated surfaces or objects.

2. What medical treatments are available for COVID-19?

Currently, there is no specific treatment or cure for COVID-19. However, supportive care such as oxygen therapy, fluids, and medications to reduce fever and pain can help manage symptoms.

3. How effective are masks in preventing the spread of COVID-19?

Wearing masks can significantly reduce the spread of COVID-19, as it helps prevent respiratory droplets from entering the air and infecting others. However, it should be combined with other preventive measures such as social distancing and hand hygiene for maximum effectiveness.

4. What are the ethical considerations surrounding vaccine development for COVID-19?

There are several ethical considerations when it comes to developing a vaccine for COVID-19, such as ensuring the safety and efficacy of the vaccine, addressing global distribution and access, and avoiding exploitation of vulnerable populations in clinical trials.

5. How can individuals protect themselves and others from COVID-19?

Individuals can protect themselves and others from COVID-19 by practicing good hygiene, such as washing hands frequently, wearing masks, and avoiding close contact with others. It is also essential to stay informed about the latest guidelines and restrictions in your area and follow them accordingly.

Suggested for: Medical Science, Medical Ethics, COVID-19