Pandemic exposes scientific rift over proving when germs are airborne

The article makes it seem as if there were only two opinions, that it is impossible to happen in any circumstance or that it is responsible for the majority of the cases. In reality it is not so.

The difference of opinion is only about how important this is for the current pandemic. Like every other infectious respiratory disease covid-19 has been very likely transmitted by aerosols, at least in some cases; but for the purposes of public health policy there is no evidence (yet?) that aerosols contribute to the spreading more often than just very rarely. This is important because measures against aerosols are much more costly and difficult, so recommending to do them could have a counterproductive effect.

If for example it becomes clear that 1 out of 10 infections are due to aerosols it would mean that there is no other way to control thee spreading and terribly strict measures would have to be put in place. But if evidence points out to 1 out of 10,000 cases being due to aerosols then there is no real point in spending a huge lot more of resources to stop only a few more cases.

Even if actual airborne transmission is minimal source control is still very important because virus is primarily transmitter via respiratory droplets.

If the general population is wearing masks droplets infecting surfaces can be kept to a minimum

Limited resources shouldn't be used as reason to limit use of masks and other ppe if there's evidence they're useful.

Entire economies have been shut down and sacrificed because of covid19, only a tiny fraction of that is needed to ensure adequate supply.

Even if actual airborne transmission is minimal source control is still very important because virus is primarily transmitter via respiratory droplets.

Airborne transmission is different from transmission by droplets. Wearing a mask is enough to importantly reduce transmission by droplets, but have minimal if any effect on aerosols.

If airborne transmission is minimal it simply do not justify investing all the resources necessary to deal with it, specially because it would mean the simple and effective measures against droplets would have to be reduced. In order to prevent one extra case you would expend the resources that right now prevent a thousand of them.

Limited resources shouldn't be used as reason to limit use of masks and other ppe if there's evidence they're useful.

Considering important airborne transmission would precisely mean to limit the use of mask and other ppe, because it would have no effect on it. Economies would have to shut down much more strictly and for longer time because isolation is the only measure that would actually be effective, and a much larger fraction of resources would be necessary to obtain the much higher degree of complexity for the ppe that is actually effective against aerosols.

For example instead of being able to buy 200 reusable coverall suits at $5, hospitals would need to buy one single hermetic and pressurized suit at $1000. That is why it is necessary to carefully determine if the transmission is by aerosols or by droplets.

Even if actual airborne transmission is minimal source control is still very important because virus is primarily transmitter via respiratory droplets.

Airborne transmission is different from transmission by droplets. Wearing a mask is enough to importantly reduce transmission by droplets, but have minimal if any effect on aerosols.

Yes, that's why I don't understand bthe reluctance ofvthe WHO to prescribe use of masks and actually discourage it given viadroplets is significant mode of transmission

I understand the great additional cost of having to use additional and much more complex /higher rated ppe, my contention is it should no longer be an issue now that more drastic and costly measures ie business lockdowns are routinely and immediately implemented by governments.

The limiter should be production capacity, not cost anymore.

Quite agree there needs to be more research to determine if and to what degree there may be transmission by aerosol.

Knee jerk reaction is not helpful and can be actually damaging.

Too late for that. The usual knee jerk reaction now is the most costly of all, lockdowns, reaction of course due to the many uncertainties about the virus.

Transmission by droplets is not one of those uncertainties though

Yes, that's why I don't understand bthe reluctance ofvthe WHO to prescribe use of masks and actually discourage it given viadroplets is significant mode of transmission

You don't understand because it is not true, the WHO has been recommending the use of masks even if the person is completely asymptomatic.

it should no longer be an issue now that more drastic and costly measures ie business lockdowns are routinely and immediately implemented by governments.

Lockdowns would also become more strict and longer lasting. even escencial business like supermarkets would become unacceptably dangerous if aerosols are an important form of transmission. What you have not yet understood is that It would not mean changing one drastic measure on some parts and the same in another, it would mean a more strict way to do things all around, from personal protection to economic lockdown.

The usual knee jerk reaction now is the most costly of all, lockdowns, reaction of course due to the many uncertainties about the virus.

You would need data to be able to qualify as knee jerk reaction something that proved extremely useful at interrupting transmission, so much that in many places it is being considered again. That still applies without aerosol transmission.

> Yes, that's why I don't understand bthe reluctance ofvthe WHO to prescribe use of masks and actually discourage it given viadroplets is significant mode of transmission

You don't understand because it is not true, the WHO has been recommending the use of masks even if the person is completely asymptomatic.

I was referring to the recommendation before, when use for general population was discouraged. Im not even sure if that has changed already

And I don't know what data you need to qualify knee jerk reaction. To qualify that a lockdown is not very useful? I wasn't aware that knee jerk reaction needs to be that to be considered nor I dispute that lockdowns aren't effective at controlling infection.

Anyway my concern primarily is about the use of masks to control droplets, I think that's clear enough from my initial post.

And why cost shouldn't be a concern considering it seems to be ok to use much more costly interventions.

Thanks for the explanations though I've learned a lot

Correct me if I am wrong:

Our understanding so far is that airborne transmission is predominantly, though not exclusively, limited by proximity. That is why social distancing and masks are so important.

Also, of prime concern is transmission by physical contact, which is why gloves, social distancing, and hand washing are so important.

The question about airborne transmission over longer distances seems to be that it is possible, but less likely outdoors than indoors.

As for testing and quarantine measures, they also are and should be part of the tool kit for response.

Last but not least, the wonderful efforts made by hospital staffs to save lives.

I was referring to the recommendation before, when use for general population was discouraged. Im not even sure if that has changed already

It has, from a long time ago, that is why I am telling you you are wrong. You know knowing something available on the news for anybody only explains why you are wrong.

And I don't know what data you need to qualify knee jerk reaction. To qualify that a lockdown is not very useful? I wasn't aware that knee jerk reaction needs to be that to be considered nor I dispute that lockdowns aren't effective at controlling infection.

Yes it is necessary, the expression is meant for a reaction done without thinking, without considering anything like evidence or rational steps. Lockdowns were carefully considered and had the expected results when done properly and strictly, just as the scientific data behind that decision predicted.

Let me be more clear, reacting quickly is not equal to a knee jerk reaction.

Anyway my concern primarily is about the use of masks to control droplets, I think that's clear enough from my initial post.

And why cost shouldn't be a concern considering it seems to be ok to use much more costly interventions.

Its the contrary, if aerosols are the main part of the problem the mask are much less useful than considered, so the control of droplets falls to a secondary concern. Cost are exactly why it is important to determine exactly how important this mechanism is, because that is what determines how to spend the limited resources in the best possible way.

Our understanding so far is that airborne transmission is predominantly, though not exclusively, limited by proximity. That is why social distancing and masks are so important.

Yes, but if aerosols are as important as some people are trying to demonstrate, social distancing and mask as done right now would simply not be enough. For example right now it is considered you can safely ride an elevator if you take care of not contaminating your hand when pressing buttons, wear a mask, ride in small number of people and don't talk. But if aerosols are more important than what we think now that elevator would still be extremely dangerous and you should not ride one until it has been extensively ventilated after every use and you change your mask for a perfect-fit N95 respirator (those that actually make breathing quite more difficult). Many places would have no real safe way to function, from offices to supermarkets and hospitals.