[BostonCard]

https://www.nytimes.com/2020/07/04/healt...borne.html

A bunch of experts write the WHO asking it to evaluate the evidence for airborne spread. "The World Health Organization has long held that the coronavirus is spread primarily by large respiratory droplets that, once expelled by infected people in coughs and sneezes, fall quickly to the floor."  That is probably true, but the word "primarily" is doing a lot of work there, and if you read more closely, the WHO has stated "airborne transmission of the virus is possible only after medical procedures that produce aerosols".  So, if a substantial proportion of cases are spread via airborne route, rather than droplets, that has very large implications.  For example, mask wearing is predicated on stopping droplets from being expelled, but it is not helpful for reducing spread of airborne particles.

But in an open letter to the W.H.O., 239 scientists in 32 countries have outlined the evidence showing that smaller particles can infect people, and are calling for the agency to revise its recommendations. The researchers plan to publish their letter in a scientific journal next week.

In my mind, the question is how much of a substantial minority of cases were due to airborne particles?  Is it like 1/3, in which case there are major repercussions.  On the other hand, if it is <5% then this is something to be aware of, but you tailor your health measures to the low hanging fruit, which is reducing droplet spread.

BC

[BostonCard]

https://www.nytimes.com/2020/07/04/healt...borne.html

A bunch of experts write the WHO asking it to evaluate the evidence for airborne spread. "The World Health Organization has long held that the coronavirus is spread primarily by large respiratory droplets that, once expelled by infected people in coughs and sneezes, fall quickly to the floor."  That is probably true, but the word "primarily" is doing a lot of work there, and if you read more closely, the WHO has stated "airborne transmission of the virus is possible only after medical procedures that produce aerosols".  So, if a substantial proportion of cases are spread via airborne route, rather than droplets, that has very large implications.  For example, mask wearing is predicated on stopping droplets from being expelled, but it is not helpful for reducing spread of airborne particles.

But in an open letter to the W.H.O., 239 scientists in 32 countries have outlined the evidence showing that smaller particles can infect people, and are calling for the agency to revise its recommendations. The researchers plan to publish their letter in a scientific journal next week.

In my mind, the question is how much of a substantial minority of cases were due to airborne particles?  Is it like 1/3, in which case there are major repercussions.  On the other hand, if it is <5% then this is something to be aware of, but you tailor your health measures to the low hanging fruit, which is reducing droplet spread.

BC

[lex24]

Great.  More confusion.  Never in my lifetime have I seen a better example of “too many chefs spoil the broth.” Seriously how many “expert” reports have been written on Covid?

At this point quite honestly I wish they all just shut up. When they actually have some real information they can impart, great. Until then BC I still go with your flatulence test. It’s as good as anything else out there

[lex24]

Great.  More confusion.  Never in my lifetime have I seen a better example of “too many chefs spoil the broth.” Seriously how many “expert” reports have been written on Covid?

At this point quite honestly I wish they all just shut up. When they actually have some real information they can impart, great. Until then BC I still go with your flatulence test. It’s as good as anything else out there

[dabigv13]

Science takes time and evolves with the data. Also, if we had listened to experts like the Koreans did, we'd be in far better shape.

[dabigv13]

Science takes time and evolves with the data. Also, if we had listened to experts like the Koreans did, we'd be in far better shape.

[BostonCard]

Lex, I understand your frustration.  I wish it weren't so.  However, this is how science progresses; it is messy and comes about in fits and starts.  Sometimes what we think we know just ain't so, and we have to update our thinking of how things are.  Unfortunately, we don't always have the luxury of waiting until a conclusive study comes around, when we have to provide advice right now, based on whatever data you have and whatever parallels you can draw to similar situations in the past.  Unfortunately, sometimes that advice is wrong, sometimes its incomplete, often times it is contradictory.

Moreover, scientific advice comes from a lot of different individuals and organizations.  So I don't think it is surprising that it will be contradictory and confusing.  Over time, something approaching a consensus will emerge, and the advice will become more consistent.  But you are going to have to bear with process as it sorts everything out.  The scientific method is a bit like democracy, the worst system of knowledge advancement, except for all the other systems that have been tried.

BC

[BostonCard]

Lex, I understand your frustration.  I wish it weren't so.  However, this is how science progresses; it is messy and comes about in fits and starts.  Sometimes what we think we know just ain't so, and we have to update our thinking of how things are.  Unfortunately, we don't always have the luxury of waiting until a conclusive study comes around, when we have to provide advice right now, based on whatever data you have and whatever parallels you can draw to similar situations in the past.  Unfortunately, sometimes that advice is wrong, sometimes its incomplete, often times it is contradictory.

Moreover, scientific advice comes from a lot of different individuals and organizations.  So I don't think it is surprising that it will be contradictory and confusing.  Over time, something approaching a consensus will emerge, and the advice will become more consistent.  But you are going to have to bear with process as it sorts everything out.  The scientific method is a bit like democracy, the worst system of knowledge advancement, except for all the other systems that have been tried.

BC

[oldalum]

Unfortunately, we don't always have the luxury of waiting until a conclusive study comes around, when we have to provide advice right now, based on whatever data you have and whatever parallels you can draw to similar situations in the past.  

YES. And often a conclusive study never comes, or when it arrives it is already outdated. Or it doesn't necessarily apply to the patient or situation in front of you.  I think people often don't realize that this is the state of a large proportion of medical care all the time; it is just made much worse and more evident by the time urgency of and public attention to the pandemic. Physicians must constantly use their judgment in determining a reasonable course of action for any specific patient.

[oldalum]

Unfortunately, we don't always have the luxury of waiting until a conclusive study comes around, when we have to provide advice right now, based on whatever data you have and whatever parallels you can draw to similar situations in the past.  

YES. And often a conclusive study never comes, or when it arrives it is already outdated. Or it doesn't necessarily apply to the patient or situation in front of you.  I think people often don't realize that this is the state of a large proportion of medical care all the time; it is just made much worse and more evident by the time urgency of and public attention to the pandemic. Physicians must constantly use their judgment in determining a reasonable course of action for any specific patient.

[Mick]

So here's a scenario...

Santa Clara County.  Sis takes her car to a car wash, recently opened.  Car goes through the wash, car emerges, four men clean the interior with the doors open for four minutes.  Sis is outside watching this the whole time.  She wipes down the car's interior with sterile wipes.  Gets in the car, shuts the door with windows rolled up and drives off.  After a few minutes, she rolls down all four windows.

Sis is wearing mask the entire time.  Four men are wearing masks the entire time.  None of the masks are medical-level.

What are the odds that Sis has been infected with COVID?  Curious because it is all that she and hubby could discuss during dinner.  Sis is convinced she's probably been infected.  Hubby thinks there's virtually no way. 

What do you think is the likelihood of infection?

[Mick]

So here's a scenario...

Santa Clara County.  Sis takes her car to a car wash, recently opened.  Car goes through the wash, car emerges, four men clean the interior with the doors open for four minutes.  Sis is outside watching this the whole time.  She wipes down the car's interior with sterile wipes.  Gets in the car, shuts the door with windows rolled up and drives off.  After a few minutes, she rolls down all four windows.

Sis is wearing mask the entire time.  Four men are wearing masks the entire time.  None of the masks are medical-level.

What are the odds that Sis has been infected with COVID?  Curious because it is all that she and hubby could discuss during dinner.  Sis is convinced she's probably been infected.  Hubby thinks there's virtually no way. 

What do you think is the likelihood of infection?

[dabigv13]

Near zero chance. Sustained exposure in a poorly ventilated space is how most transmission occurs. The air in this scenario would be circulated too quickly. She wiped down so reduced the already low odds of fomite transmission. Even if nobody was wearing masks, this would be pretty safe.

Driving in a car with someone else with the windows up for 15 minutes would be a concern. But not the scenario you're describing.

[dabigv13]

Near zero chance. Sustained exposure in a poorly ventilated space is how most transmission occurs. The air in this scenario would be circulated too quickly. She wiped down so reduced the already low odds of fomite transmission. Even if nobody was wearing masks, this would be pretty safe.

Driving in a car with someone else with the windows up for 15 minutes would be a concern. But not the scenario you're describing.

[BostonCard]

https://wwwnc.cdc.gov/eid/article/26/9/2...32083#tnF1

Patient B1.1 was the downstairs neighbor of case-patient A0. They used the same elevator in the building but not at the same time and did not have close contact otherwise.

This would support either airborne transmission or transmission via fomites.  The transmission generated a cluster of at least 71 cases.

BC

[BostonCard]

https://wwwnc.cdc.gov/eid/article/26/9/2...32083#tnF1

Patient B1.1 was the downstairs neighbor of case-patient A0. They used the same elevator in the building but not at the same time and did not have close contact otherwise.

This would support either airborne transmission or transmission via fomites.  The transmission generated a cluster of at least 71 cases.

BC

[akiddoc]

So here's a scenario...

Santa Clara County.  Sis takes her car to a car wash, recently opened.  Car goes through the wash, car emerges, four men clean the interior with the doors open for four minutes.  Sis is outside watching this the whole time.  She wipes down the car's interior with sterile wipes.  Gets in the car, shuts the door with windows rolled up and drives off.  After a few minutes, she rolls down all four windows.

Sis is wearing mask the entire time.  Four men are wearing masks the entire time.  None of the masks are medical-level.

What are the odds that Sis has been infected with COVID?  Curious because it is all that she and hubby could discuss during dinner.  Sis is convinced she's probably been infected.  Hubby thinks there's virtually no way. 

What do you think is the likelihood of infection?

The likelihood of infection is pretty low, but she could lower it to zero by going to a drive through car wash and not allowing anyone else enter the vehicle.

[akiddoc]

So here's a scenario...

Santa Clara County.  Sis takes her car to a car wash, recently opened.  Car goes through the wash, car emerges, four men clean the interior with the doors open for four minutes.  Sis is outside watching this the whole time.  She wipes down the car's interior with sterile wipes.  Gets in the car, shuts the door with windows rolled up and drives off.  After a few minutes, she rolls down all four windows.

Sis is wearing mask the entire time.  Four men are wearing masks the entire time.  None of the masks are medical-level.

What are the odds that Sis has been infected with COVID?  Curious because it is all that she and hubby could discuss during dinner.  Sis is convinced she's probably been infected.  Hubby thinks there's virtually no way. 

What do you think is the likelihood of infection?

The likelihood of infection is pretty low, but she could lower it to zero by going to a drive through car wash and not allowing anyone else enter the vehicle.

[BostonCard]

The CDC has now updated its guidance about airborne spread:

[tweet]https://twitter.com/axios/status/1313183018673213440?s=20[/tweet]

BC

[BostonCard]

The CDC has now updated its guidance about airborne spread:

[tweet]https://twitter.com/axios/status/1313183018673213440?s=20[/tweet]

BC

[magnus]

I fear this guidance will revert in a couple days. The CDC hasn't been very good about consistent messaging. =/

[magnus]

I fear this guidance will revert in a couple days. The CDC hasn't been very good about consistent messaging. =/