Presymptomatic June 9, 2020

 Commenter 1: My understanding is that its because symptoms can take up to two weeks to show up.

If we AGGRESSIVELY contact trace then we dont need to restrict society, but no one is comfortable with that level of intrusion either

Commenter 2: Jesus, this is where you have to be so fucking careful with headlines. ASYMPTOMATIC is not the same as PRESYMPTOMATIC. You are absolutely able (and likely) to catch this virus from someone who is not presenting symptoms at the instant of interaction.

@Commenter 2: In terms of presymptomatic having the ability to transmit the virus, what do you think of this from BC’s deputy provincial health officer Dr Reka Gustafson, June 1, 2020 ?

“There is absolutely no evidence that this disease is airborne, and we know that if it were airborne, then the measures that we took to control COVID-19 would not have worked,” Dr. Reka Gustafson, B.C.’s deputy provincial health officer, told CTV Morning Live Monday.
“We are very confident that the majority of transmission of this virus is through the droplet and contact route.”
Gustafson explained that airborne diseases – like measles or chickenpox – have a different way of transmission.
“The overwhelming majority of (COVID-19) transmissions occur through close, prolonged contact and that is not the pattern of transmission we see through airborne diseases,” she said.
The BC Centre for Disease Control explains airborne transmission happens when small, evaporated droplets float in the air for a long period of time. In the case of droplets, however, they typically only spread a couple of metres before falling to the ground.
The confusion, Gustafson said, is that droplets of the virus can be in theory be aerosolized in a lab, but that’s not how it typically spreads in the real world. “

So if someone is not showing any symptoms 2-14 days before symptoms appear, how does this droplet/contact transmission occur?
https://www.ctvnews.ca/mobile/absolutely-no-evidence-that-covid-19-is-airborne-b-c-health-official-says-1.4964156

Commenter 2: This boils down again to the difference between how the academic field and the general public communicate. This scientist is doing a particularly poor job of it. There is a scientific definition of the word “airborne” that differs slightly from what your intuition might suggest, and it has mostly to do with the size of the particles.

Every time you are speaking, breathing, and especially singing, you are expelling droplets of bodily fluids into the air, and they are going to fall in a mist all around you. If you’re speaking closely to someone, at a microscopic level you are basically spitting in their face the entire time, and you are absolutely shedding viral load in the presymptomatic phase of this infection. Those droplets could enter through direct contact with the eye, or perhaps just fall onto their hand, or even their clothing, and work their way back up to a mucous membrane and then into the system.

Commenter 2: Think of it like if every time someone took a breath, they expelled a cloud of glitter instead of air. Transmission occurs every time a piece of that glitter makes it to your eye, your nose, your mouth, or your more sensitive bits, before the timer runs out. And that timer is anywhere from seven minutes to seventeen days, depending on the environment.

@Commenter 2: In this opinion by Ed Ballard, a professional opera, concert, and choral singer. He writes:
“And, despite the fact that Freiburg has since withdrawn the guidelines and released new advice that singing can be safe, provided social distancing is in place, the old guidelines are still being shared.
TWO misconceptions continue to dominate. First, that singing produces large quantities of aerosol particles, which would soon engulf any enclosed space. Second, that singing projects both droplet and aerosol particles at a far greater rate than other activities.
Singing may, indeed, produce aerosol particles. But, according to the World Health Organization (WHO), Covid-19 is not an airborne virus. “In an analysis of 75,465 Covid-19 cases in China”, one of its scientific briefs states, “airborne transmission was not reported.” “There is no evidence of transmission of the virus as an airborne pathogen,” the WHO’s technical lead on infection prevention and control, Dr Benedetta Allegranzi, has said, despite theories based on lab simulations. Droplet and contact transmission remains the WHO’s official position, as it does of Public Health England.”—So, here Ballad feels that even though singing produces aerosol particles, he doesn’t not equate these aerosol particles to droplets that can pass on transmission.
https://www.churchtimes.co.uk/articles/2020/5-june/comment/opinion/it-is-time-to-sing-again

@Commenter 2: Continuing from the article:“The idea that singing leads to a vastly increased projection of either droplets or aerosols has also been called into question.
A recent study by the Institute of Fluid Mechanics and Aerodynamics, in Munich, looked specifically at the disturbance of air caused by singing and wind instruments.
The study found that it was “only set in motion in the immediate vicinity of the mouth when singing”. The experiments that they carried out showed that “at a distance of around 0.5 m, almost no air movement can be detected, regardless of how loud the sound was and what pitch was sung”.
Studies commissioned by the Vienna Philharmonic and the Bamberg Symphony Orchestra reached the same conclusion for orchestral players. All the studies stress the importance of social distancing. But the singing, or playing, itself was not the problem.
Professional choirs in Europe have been quick to adapt. Opera companies have begun announcing full autumn seasons, and concerts and recitals, behind closed doors, are already taking place, even in London. Clearly, there is already scope for voices to be lifted in song.”

@Commenter 2: “The low spread of air movement is not surprising, since singing does not expel a large volume of air in jerks like coughing or sneezing [6, 7]. Rather, the art of singing is to move as little air as possible and still produce a beautiful and powerful sound.”

“The fact is that the 1 µm droplets in the aerosol have already completely evaporated after fractions of a second [11, 12]. Droplets with a diameter of 10 μm are completely evaporated after about 1 second (at 50% relative humidity) and very large droplets sink quickly to the ground and evaporate [13, 14, 15].
It is very important to realize that those experiments, in which the ability of viruses to reproduce in aerosols was studied, were carried out in a laboratory condition that is completely unrealistic in practice.[16]
There the rate of evaporation was in equilibrium with the rate of condensation. These conditions may apply in the steam bath, the shower and in some kitchens without proper steam extraction and therefore in some tiny restaurants, but not in our natural environment.”
https://www.unibw.de/lrt7-en/making_music_during_the_sars-cov-2_pandemic.pdf

@Commenter 2: You assert that “you are absolutely shedding viral load in the presymptomatic phase of this infection.”
I wonder if there are any studies backing that up? Or any sources you care to share with me regarding that?

Commenter 2: Statistical data that is modelled from China is unfortunately less than the gold standard right now. As for the fluid dynamics study I’m highly skeptical since the introduction of the paper is principally an economic argument, which immediately suggests bias. I’m reading the rest of it now.

Commenter 2: This point hasn’t really been widely argued since the first report, but a quick google search produced one statistically relevant study that seems to be currently referenced:

https://www.nejm.org/doi/full/10.1056/NEJMoa2008457

I’m sure there are others. Have you looked through some of the pre-print servers?

@Commenter 2: I had a brief look at the study you just linked. Some observations I would make:

1. It looks at an older population at a skilled nursing facility. How can we rule out co-morbidities and weaker immune system/vitamin D levels?

2. When I look at their statement and their references for their statement:”A key factor in the transmissibility of Covid-19 is the high level of SARS-CoV-2 shedding in the upper respiratory tract,1 even among presymptomatic patients, which distinguishes it from SARS-CoV-1, where replication occurs mainly in the lower respiratory tract.2 Viral loads with SARS-CoV-1, which are associated with symptom onset, peak a median of 5 days later than viral loads with SARS-CoV-2, which makes symptom-based detection of infection more effective in the case of SARS CoV-1.3″ – I just don’t see any hard scientific studies proving what they just said.

Reference 1 is preprint, so not good science yet.
Reference 2 is back in 2004 for SARS1.
Reference 3 is an observational cohort study in 2 hospitals of a small sample size of 30 patients.
Reference 5 was again in a skilled nursing facility (related to the same one as study 1?) and what I interpret as having a non-conclusion ending (“most likely contributed to…”). “Most likely” is not very conclusive:
“Rapid and widespread transmission of SARS-CoV-2 was demonstrated in this skilled nursing facility. More than half of residents with positive test results were asymptomatic at the time of testing and most likely contributed to transmission. Infection-control strategies focused solely on symptomatic residents were not sufficient to prevent transmission after SARS-CoV-2 introduction into this facility.”

And given WHO’s June 8 initial press release that there’s no asymptomatic transmission, then I might even say that Reference 5 (“most likely contributed to transmission”) would be contrary to BC Chief Medical Health Officer and the asymptomatic study with 455 folks.

I haven’t had time to thoroughly critique the study you just linked, but my sense is that if it has any applicability, it is only for older populations in skilled nursing facilities.

Commenter 3: Asymptomatic isn’t the same as the incubating period before symptoms happen. If you are infected, and not showing symptoms YET, because it can take up to 2 weeks, you can spread the heck out of the virus.

While social distancing sucks for many reasons, I’m happy we did that here – because the numbers show in places that didn’t, just how well that went. People sick and dying in droves.

Commenter 3B: Apparently WHO is not the best at communicating information well. Here is a quote from a science person regarding this article. Please continue wearing your mask or whatever other measures that our health officers are encouraging us to do so that we don’t have another outbreak:

I’m about to make a lot of people sad, and for that I apologize, but the science communicator in me feels compelled to address this.

You might be seeing a headline today saying that asymptomatic people aren’t spreading COVID.

Unfortunately, WHO is absolutely terrible at clear science communication. There is an important difference between asymptomatic and PREsymptomatic.

The very tiny, vanishingly-small, minuscule percentage of people who get COVID and never ever show symptoms at any point are the ones who are not driving the spread of COVID. This is very, very few people. Which is why they aren’t the ones “driving” the spread.

The very LARGE MAJORITY of people who incubate COVID for 2-14 days before showing symptoms (and possibly make contact with others during the time when they have no symptoms and don’t yet know they are sick) are VERY MUCH driving the spread of COVID. This is the case for most people who test positive; many don’t have symptoms at first, possibly not even at the point of testing, because COVID has a very long incubation period. But most do go on to have symptoms at SOME point. And even before they are symptomatic, when a layperson might describe them as “asymptomatic,” they are still very much contagious, and still very much responsible for most of the spread, just as we previously understood.

It’s hard to watch people get their hopes up once you understand the actual info that WHO clearly failed to communicate, and scary to think that people might make decisions based on an erroneous understanding of the scientific reality.

Stay safe. Wear your mask. Wash your hands. Don’t touch your face. And keep staying home as much as you can. I’m sorry.

@Commenter 3B: Here’s a recent study that shows 455 folks exposed to an asymptomatic SARS-CoV-2 carrier did not get it.
https://www.sciencedirect.com/science/article/pii/S0954611120301669

Commenter 3B: Asymptomatic isn’t pre-symptomatic. The number of asymptomatic folks is very small. So of course transmissions will be minimal. Based on numbers alone.

Commenter 4: That study follows just one potential asymptomatic carrier, which is hardly conclusive. A study of one individual like this is not typically used to draw a general conclusion.

Even the conclusion paragraph on the summary page steers clear of declaring all asymptomatic carriers won’t transmit the disease:

“In summary, all the 455 contacts were excluded from SARS-CoV-2 infection and we conclude that the infectivity of some asymptomatic SARS-CoV-2 carriers might be weak.”

@Commenter 3B: You made a statement above that a very large majority of people who incubate SARS-CoV-2 for 2-14 days before showing symptoms … are very much driving the spread of covid.

What do you think of this from BC’s deputy provincial health officer Dr Reka Gustafson, June 1, 2020 ?



“There is absolutely no evidence that this disease is airborne, and we know that if it were airborne, then the measures that we took to control COVID-19 would not have worked,” Dr. Reka Gustafson, B.C.’s deputy provincial health officer, told CTV Morning Live Monday.

“We are very confident that the majority of transmission of this virus is through the droplet and contact route.”

Gustafson explained that airborne diseases – like measles or chickenpox – have a different way of transmission.

“The overwhelming majority of (COVID-19) transmissions occur through close, prolonged contact and that is not the pattern of transmission we see through airborne diseases,” she said.

The BC Centre for Disease Control explains airborne transmission happens when small, evaporated droplets float in the air for a long period of time. In the case of droplets, however, they typically only spread a couple of metres before falling to the ground.

The confusion, Gustafson said, is that droplets of the virus can be in theory be aerosolized in a lab, but that’s not how it typically spreads in the real world. “



So if someone is not showing any symptoms 2-14 days before symptoms appear, how does this droplet/contact transmission occur?

@Commenter 4: Thanks for your input. You’re saying that just testing what happens with one asymptomatic carrier is not indicative enough and that the conclusion is not conclusive.

What do you think when you also consider what Dr. Reka Gustafson, B.C.’s deputy provincial health officer said on June 1, 2020?



“There is absolutely no evidence that this disease is airborne, and we know that if it were airborne, then the measures that we took to control COVID-19 would not have worked,” Dr. Reka Gustafson, B.C.’s deputy provincial health officer, told CTV Morning Live Monday.

“We are very confident that the majority of transmission of this virus is through the droplet and contact route.”

Gustafson explained that airborne diseases – like measles or chickenpox – have a different way of transmission.

“The overwhelming majority of (COVID-19) transmissions occur through close, prolonged contact and that is not the pattern of transmission we see through airborne diseases,” she said.

The BC Centre for Disease Control explains airborne transmission happens when small, evaporated droplets float in the air for a long period of time. In the case of droplets, however, they typically only spread a couple of metres before falling to the ground.

The confusion, Gustafson said, is that droplets of the virus can be in theory be aerosolized in a lab, but that’s not how it typically spreads in the real world. “

Your thoughts are appreciated.

Commenter 4: We’re talking about asymptomatic transmission, not airborne transmission. I don’t see the connection.

Commenter 3B: I remember reading this article. What I took away from it was that to prevent droplet spread, that a mask is still useful.

For example, I have allergies. So I’m a bit of a sneezy person to begin with. If I did get it, even before I knew it, I’m definitely spraying that around without a mask. And our guidelines kept people out of close quarters.

Diseases are very interesting. Spread depends on so many factors. We’re still learning about this one. Airborn or not is one factor. They’re still nailing down what frequency, or how long of contact for example affects transmission rates. It’s why they say you can go for a walk outside without your mask and if you’re just passing people walking, even if they’re infected, you very likely won’t get it. Compared to longer exposure or in closer quarters.

I’m excited (in a science way) to see exactly what the parameters are tbh, so that we can have firmer ‘rules’ or guidelines as to how to navigate the disease effectively with as much freedom and enjoyment of life as possible if you know what I mean.

The cool thing about scientists, is that they are willing to change their opinion as new data rolls in. New guidelines will emerge that are better and better as time goes on.

@Commenter 3B: Sorry to hear about the allergies. No fun ;-(

Sneezing, I’m pretty sure, produces droplets. I agree with you that just passing people walking is an unvery likely way of transmission. It needs to be droplet contact in close quarters.

The longer exposure is still unclear in my mind. I wonder if a longer time in the vicinity of an active symptomatic SARS-CoV-2 person may just increase the probability of getting droplet contact. But droplet contact seems to be essential.

@Commenter 4: Correct you are that transmission is not airborne.

I wanted to point out that BC’s medical health director Dr Reka Gustafson said:

“We are very confident that the majority of transmission of this virus is through the droplet and contact route.”

“The overwhelming majority of (COVID-19) transmissions occur through close, prolonged contact and that is not the pattern of transmission we see through airborne diseases,”

Leave a Reply

Your email address will not be published. Required fields are marked *