Battle Rages Inside Hospitals Over How COVID Strikes and Kills: Aerosols or Droplets

Lambert here: This piece appeared after the CDC had removed its draft on aerosols from its website, but before the final version, reinstating aerosols, was published. That doesn’t affect the content of the piece. Readers know my views on this topic, so there’s no need to repeat them. However, I would b very interested to hear from any hospital workers in the readership on how their workplace is handling the issue.

By Robert Lewis and Christina Jewett of Kaiser Health News. Originally published at Kaiser Health News.

Front-line health care workers are locked in a heated dispute with many infection control specialists and hospital administrators over how the novel coronavirus is spread ― and therefore, what level of protective gear is appropriate.

At issue is the degree to which the virus is airborne ― capable of spreading through tiny aerosol particles lingering in the air ― or primarily transmitted through large, faster-falling droplets from, say, a sneeze or cough. This wonky, seemingly semantic debate has a real-world impact on what sort of protective measures health care companies need to take to protect their patients and workers.

The Centers for Disease Control and Prevention injected confusion into the debate Friday with guidance putting new emphasis on airborne transmission and saying the tiny aerosol particles, as well as larger droplets, are the “main way the virus spreads.” By Monday that language was gone from its website, and the agency explained that it had posted a “draft version of proposed changes” in error and that experts were still working on updating “recommendations regarding airborne transmission.” [Guidance supporting aerosol and droplet transmission were subsequently published by CDC. –lambert]

Dr. Anthony Fauci, the top U.S. infectious disease expert, addressed the debate head-on in a Sept. 10 webcast for the Harvard Medical School, pointing to scientists specializing in aerosols who argued the CDC had “really gotten it wrong over many, many years.”

“Bottom line is, there’s much more aerosol [transmission] than we thought,” Fauci said.

The topic has been deeply divisive within hospitals, largely because the question of whether an illness spreads by droplets or aerosols drives two different sets of protective practices, touching on everything from airflow within hospital wards to patient isolation to choices of protective gear. Enhanced protections would be expensive and disruptive to a number of industries, but particularly to hospitals, which have fought to keep lower-level “droplet” protections in place.

The hospital administrators and epidemiologists who argue that the virus is mostly droplet-spread cite studies that show it spreads to a small number of people, like a cold or flu. Therefore, N95 respirators and strict patient isolation practices aren’t necessary for routine care of COVID-19 patients, those officials say.

On the other side are many occupational safety experts, aerosol scientists, front-line health care workers and their unions, who are quick to note that the novel coronavirus is far deadlier than the flu ― and argue that the science suggests that high-quality, and costlier, N95 respirators should be required for routine COVID-19 patient care.

The highly protective respirators have been in short supply nationwide and have soared in price, from about $1 to $7 each. Meanwhile, research has shown high rates of asymptomatic virus transmission, putting N95s in high demand among front-line health care workers in virtually every setting.

The debate has come to a head at hospitals from coast to coast, as studies have emerged showing that live virus hangs in COVID-19 patients’ hospital rooms even in the absence of “aerosol-generating” procedures (such as intubations or breathing treatments) and has contributed to outbreaks at a nursing home, shuttle bus and choir practice.

KHN and The Guardian U.S. are examining more than 1,200 health care worker deaths from COVID-19, including many in which their family or colleagues reported they worked with inadequate personal protective gear.

Yet some front-line workers and managers disagree about exactly how and why health care workers are getting sick.

The hospital infection-control and epidemiology leaders cite studies suggesting that many health care workers are contracting the virus outside of work and at rates that mirror what’s happening in their communities.

A group of Penn Medicine epidemiologists in late July characterized research on aerosol transmission as unconvincing and cited “extensive published evidence from across the globe” showing the “overwhelming majority” of coronavirus spread is “via large respiratory droplets.”

Unions, occupational health researchers and aerosol scientists, though, reference another pile of studies showing health care workers have been hit far harder than average people ― and a study that showed active viral particles can drift in the air up to 15 feet from a patient in a hospital room. Such particles can hang in the air for up to three hours.

Backing their concerns, a July 6 letter signed by 239 scientists urged the medical community and World Health Organization to recognize “the potential for airborne spread of Covid-19.”

The letter pointed to studies that say talking, exhaling and coughing emit tiny particles that remain suspended in the air far longer than droplets and “pose a risk of exposure.”

In one ward of a Dutch nursing home with recirculated air, researchers found that 81% of the residents were diagnosed with COVID-19. Half of the workers on the ward ― who all wore surgical masks during patient care but not during breaks ― also tested positive for the virus.

Although researchers couldn’t exclude transmission by another method, the “near-simultaneous detection” of the virus among nearly all the residents pointed to aerosol spread.

The idea that the virus is spread by either droplets or aerosols is an oversimplification, said Dr. Shruti Gohil, associate medical director of epidemiology and infection prevention at the University of California-Irvine School of Medicine.

Gohil said it’s more of a spectrum, with the virus being transmitted by some droplets and some large aerosol particles as well.

One metric people in the hospital infection-control field focus on, though, is how many people one sick person infects. For COVID-19, research has shown that the number is about two ― similar to a cold or the flu. For an unequivocally airborne disease like measles, the number is closer to 12 to 18.

Measles is “what airborne [transmission] looks like,” Gohil said. “If this was truly a primary aerosol-transmissible disease, we’d be in a world of hurt.”

Hospital epidemiologists are also focused on the rate of household spread of the novel coronavirus. With the measles, the risk of an unvaccinated member of a household getting sick is 85%, said Dr. Rachael Lee, a hospital epidemiologist and assistant professor at the University of Alabama-Birmingham. For COVID-19, she said, the risk is closer to 10%.

Though the virus is believed to be spread more by droplets than aerosol particles, Lee said, staffers at UAB University Hospital wear an N95 respirator for an extra layer of protection and because the patients require so many breathing treatments or procedures considered “aerosol-generating.”

Such practices are not universal. At the University of Iowa’s hospital, health care workers use N95s and face shields for aerosol-generating procedures but otherwise use surgical masks and face shields for routine care of COVID patients, said Dr. Daniel Diekema, director of the division of infectious diseases at the university.

He said such “enhanced droplet precautions” are working. Places where workers are correctly using regular medical masks and face shields are finding no significant spread of the disease among staffers, although one such report focused on the spread from a single patient.

Elsewhere, patients have also been safe on floors where COVID-19 patients and those without the virus have been placed in adjacent rooms ― a practice those concerned about aerosol spread do not endorse.

“It’s not an airborne disease the way measles or tuberculosis is,” said Dr. Shira Doron, an epidemiologist at Tufts Medical Center in Boston and an assistant professor at Tufts medical school. “We know because we don’t see outbreaks that affect multiple patients on a floor.”

Origin of the Debate

The CDC helped set the stage for the current debate. In March, the agency issued revised guidance essentially saying it was “acceptable” for health care workers to use surgical masks ― instead of N95s ― for routine care. The guidance said respiratory droplets were the most likely source of transmission and recommended N95s only for aerosol-generating procedures.

“The contribution of small respirable particles, sometimes called aerosols or droplet nuclei, to close proximity transmission is currently uncertain. However, airborne transmission from person-to-person over long distances is unlikely,” according to the guidance.

The California Hospital Association sent a letter to the state’s congressional delegation urging the revised guidance be made permanent.

“We need the CDC to clearly, not conditionally, move from airborne to droplet precautions for patients and health care workers,” the letter said. Doing so would enable hospitals to preserve PPE supplies and limit the use of special isolation rooms for COVID patients.

An association spokesperson told KHN that the group wasn’t weighing in on the science, merely pressing for clarity of the rules.

Christopher Friese, professor of nursing, health management and policy at the University of Michigan, is among the experts who think those rules have endangered health care workers.

“We lost a tremendous amount of time and, candidly, lives because the early guidance was to wear N95s only for those specific procedures,” Friese said.

Family members and union leaders from Missouri to Michigan to California have raised concerns about nurses dying of COVID-19 after caring for virus patients without N95 respirators. In such cases, hospitals have said they followed CDC guidance.

Friese echoed some occupational safety experts who suggested stronger guidance from the CDC early on calling the disease airborne might have had an impact ― perhaps pressuring President Donald Trump to invoke the Defense Production Act to boost supplies of N95s so “we might have the supply we need everywhere we need,” Friese said.

Surveys across the country show there’s still a shortage of personal protective equipment at many health care facilities.

The CDC guidance posted Friday would have put pressure on some hospitals to bolster their protective measures, something they have reportedly resisted. It said the virus can spread when a person sings, talks or breathes.

“These particles can be inhaled into the nose, mouth, airways, and lungs and cause infection,” the site said. “This is thought to be the main way the virus spreads.”

By Monday morning, the website was back to saying the virus mainly spreads through droplets, noting that draft language had been posted in error.

The University of Nebraska Medical Center has been taking so-called airborne precautions from the start. There, Dr. James Lawler, a physician and director of the Global Center for Health Security at the university, said his colleagues documented that the virus can drift in the air and live on surfaces at an extensive distance from patients.

He said the hospital tests all admitted patients for the virus and keeps COVID-19 patients apart from the general population. He said they pay close attention to cleaning shared spaces and monitoring airflow within the restricted-access unit. Workers also had N95 respirators or PAPRS, which are fitted hoods with filtered air pumped in.

All of it has added up to a “very low” rate of health care worker infections.

Amid uncertainty about the virus, and as an unprecedented number of health care workers are dying, adopting the “highest possible” forms of protection seems the best course, said Betsy Marville, nurse organizer for the 1199SEIU United Healthcare Workers East union in Florida.

That would mean a departure from CDC guidelines that now say health care workers need an N95 respirator only for “aerosol-generating” procedures, like intubations or other breathing treatments. She said the rule has left the nurses she represents in Florida scrambling for protective gear ― or unprotected ― when patients need such treatments urgently.

“You don’t leave your patient in distress and go looking for a mask,” she said. “That’s crazy.”

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About Lambert Strether

Readers, I have had a correspondent characterize my views as realistic cynical. Let me briefly explain them. I believe in universal programs that provide concrete material benefits, especially to the working class. Medicare for All is the prime example, but tuition-free college and a Post Office Bank also fall under this heading. So do a Jobs Guarantee and a Debt Jubilee. Clearly, neither liberal Democrats nor conservative Republicans can deliver on such programs, because the two are different flavors of neoliberalism (“Because markets”). I don’t much care about the “ism” that delivers the benefits, although whichever one does have to put common humanity first, as opposed to markets. Could be a second FDR saving capitalism, democratic socialism leashing and collaring it, or communism razing it. I don’t much care, as long as the benefits are delivered. To me, the key issue — and this is why Medicare for All is always first with me — is the tens of thousands of excess “deaths from despair,” as described by the Case-Deaton study, and other recent studies. That enormous body count makes Medicare for All, at the very least, a moral and strategic imperative. And that level of suffering and organic damage makes the concerns of identity politics — even the worthy fight to help the refugees Bush, Obama, and Clinton’s wars created — bright shiny objects by comparison. Hence my frustration with the news flow — currently in my view the swirling intersection of two, separate Shock Doctrine campaigns, one by the Administration, and the other by out-of-power liberals and their allies in the State and in the press — a news flow that constantly forces me to focus on matters that I regard as of secondary importance to the excess deaths. What kind of political economy is it that halts or even reverses the increases in life expectancy that civilized societies have achieved? I am also very hopeful that the continuing destruction of both party establishments will open the space for voices supporting programs similar to those I have listed; let’s call such voices “the left.” Volatility creates opportunity, especially if the Democrat establishment, which puts markets first and opposes all such programs, isn’t allowed to get back into the saddle. Eyes on the prize! I love the tactical level, and secretly love even the horse race, since I’ve been blogging about it daily for fourteen years, but everything I write has this perspective at the back of it.


  1. Shiloh1

    In a hospital or assisted living setting there are worse means / orifices of expelling bad stuff from a patient’s body than a sneeze or cough, if you know what I mean and I think you do.

    Sometimes the same people helping with that part are also helping out with the chow.

  2. Samuel Conner

    The discounting of aerosol transmission of viruses is long-standing (per some items linked at NC recently, citing century-old writings and pronouncements of an expert whose name I don’t recall).

    It’s a bit disheartening to think that new hospital design for the past century may have been premised on an error. I imagine that there may be significant institutional resistance to changes in understanding of disease transmission, on account of the huge sunk cost of current infrastructure and the high cost of reconfiguring ventilation systems.

    Perhaps this argument will be ongoing when the next aerosol-transmitted viral epidemic strikes.

    1. anon in so cal


      Starting in 1910, the dogmatic view held that droplets, and not aerosols, were the main mode of transmission.

      “There is a huge bias embedded in the field of medical infectious diseases since around 1910. It is assumed that droplet infection is obvious and thus needs no strong evidence. For example, it was assumed to be major for SARS-CoV-2 despite a near complete lack of evidence, which continues to this day. On the other hand it is assumed that aerosol infection is extremely unlikely. Since “extraordinary claims require extraordinary evidence,” aerosol transmission continues to be downplayed or minimized despite overwhelming evidence that it is much more important than droplet transmission for SARS-CoV-2.

      The bias originated with the work of Dr. Charles Chapin, and in particular his seminal book in 1910, The sources and modes of infection. Chapin was a very influential public health researcher, and e.g. served as the president of the American Public Health Association in 1927.

      In his book he reviewed 50 years of accumulated evidence (since germ theory was demonstrated by Pasteur in the 1860s) about how germs were transmitted for various diseases, e.g through air, water, hands, food, soil, etc. He realized that respiratory diseases were transmitted most easily in close proximity, and that social distance reduced infection (he calls it “contact infection”, but often actual contact is not required, so we prefer to discuss it as “infection in close proximity”). That is an empirical observation, which is correct. It is the reason why we socially distance ourselves to avoid COVID-19 infection, and it has been shown to work very well against many respiratory diseases. Chapin was very successful in applying those principles in his new hospital in Providence, which helped increase his influence in the field of Public Health.”

  3. a different chris

    Of course this is America, so the argument isn’t so much about the transmission method as people that think supplying the troops with a N95 mask is just too damn much money to spend on the plebes.

    It also deflects from the fact that we can’t seem to manufacture said masks in any quantity.

    1. drumlin woodchuckles

      But since the elites dare not say that out loud where any potentially armed plebes might hear it, the argument is disguised in a beautiful perfume disguise as being about which way the viruses are “actually spread”.

      It is an Aztec blood sacrifice imperative disguised as a scientific argument. Which is one more factor leading to the universal social solvent of ubiquitous omni-distrust rising in every sector of society.

  4. TimH

    Call me cynical, but hospitals want to side with the tranmission vector that costs the least to reasonably PPE and otherwise protect from.

    1. Aumua

      Still missing: a clear definition of what a droplet is, and what an aerosol (droplet) is. You would think if they wanted to dispel confusion around this topic that they would be clear about that, yet here it is months later debating this topic and we till have entire stories which just brush over that information.

      1. Zamfir

        Conceptually, I think the definition is clear? A droplet (in this context) is meant as a particle that moves in an approximation of ballistic flight, with gravity strong enough that the particle falls down to the ground.

        An aerosol consists of suspended particles, so small that they won’t reach the ground in a relevant time frame. These will spread much like a gaseous contaminant.

        There is a grey area in between. Particles that would fall slowly but surely in still air conditions, but may stay suspended in stronger air movements.

        This grey area is not grey because of some lack of clear definitions. A simple 2 category model simply has its limits, and no definition will improve that.

        In indoors conditions, that grey area covers roughly particles from 10um to 100um (note: that’s a 1000fold difference in particle mass!). What seems to happen, is that medical procedures force a strict 2 category division, and traditionally that division would categorize the grey area as “droplet”.

        Now people say (correctly) that this is wrong, but that creates a whiplash effect. If there are only 2 categories, the only alternative is to count the whole grey area as “aerosol”, and that’s not quite right either.
        There seems to be a complicating factor. Traditional “airborne” diseases also require only small exposures to transmit. That means that the particle flow can be dilluted many times while staying dangerous.

        That does not appear the case for covid – the typical transmission is about sustained, close contact between people, and distance is very effective in reducing transmission. Medical people call that “droplet” behaviour, even if the actual mechanism might be closer to “suspended particles but only in fairly high concentration” . Because the medical people don’t care primarily about the actual mechanism involved, they want to skip that step and focus on the practical effects.

    2. rd

      That was the conclusion I came to back around May-June after reviewing a lot of information I could find. It continues to be reinforced by new information I see. Unfortunately, the US seems to be unable to operate in anything other than a binary on-off light switch mode instead of using dimmer switches with information and decision-making.

      My view for months has been that the primary route of transmission causing really bad cases is likely to be droplets that can provide a high viral load very quickly to the unlucky recipient.

      A secondary, but significant and more frequent transmission route is aerosols that can cause varying degree of infection depending on how concentrated and how long the exposure is. So being in a choir practice in a poorly ventilated space for a long time becomes equivalent to getting whacked with droplets. Poorly ventialted noisy bars would be similar. On the other hand, well-spaced individuals with some decent ventilation/filtration may get much lower loads and therefore the cases tend to be not as bad. Similarly, masks reduce emissions and inhalation which also reduces the severity of the cases (original paper on masks by Capps from early 1918 before Spanish Flu is here: .

      So our family has been following the following procedures:

      1. Avoid sick people.
      2. Avoid close contact with people, especially if they are unmasked.
      3. Don’t go into poorly ventilated busy indoor spaces.
      4. Use good hygiene and masking going into indoor spaces with low density, high ceilings, and decent ventilation.
      5. If we are going to be in an indoor space with other people for any significant duration, make sure that everybody has masks, the space is well ventilated or provide our own (inexpensive HEPA air purifiers properly sized for the space to provide at least 4 air changes per hour and preferably 6 or more).
      6. Hand washing and hand sanitizer is essential at key points before, during, and after interactions with non-porous surfaces that may have been touched by other people or subjected to droplets or aerosols.

      All medical staff coming into close contact with potential covid patients should have new, clean N95 masks. If they are going to be in spaces with covid patients for extended periods of time, they should have new clean N95 masks. I think the high rates of serious illness and deaths in medical staff is because they are subjected to both droplets and concentrated aerosols for extended periods of time without adequate PPE. At this point, that is criminal negligence on the part of the governments and institutions if it is continuing.

  5. Diuretical

    Droplet / aerosol is a dichotomy imposed on a continuum and a more subtle and relaxed take on the matter is that COVID, like all viruses, is a bit of both, but in its infectiousness tilts towards droplets. Aerosols probably do matter in enclosed spaces with a number of people talking / singing or one heavy shedder breathing with poor air exchanges, or in the context of AGMP (aerosol generating medical procedures), but outside of those, enhanced droplet precautions seem to work very well. There is quite a bit of published data on HCW transmission at this point, and the transmission numbers are very low if health care workers just have the droplet gear and use it consistently. I say this as someone who provides front line care. I am quite confident with surgical mask/gown/gloves/goggles, floors set to negative ventilation, and being very meticulous.

    1. grayslady

      I say this as someone who provides front line care. I am quite confident with surgical mask/gown/gloves/goggles, floors set to negative ventilation, and being very meticulous.

      This is pretty much what my pulmonologist told me. Since he is also board certified in Critical Care and Internal Medicine, he’s been on the front lines at one of our local hospitals. He said no one was wearing, as he put it, the “space suit” gear that has been shown on tv. Rather, everyone was simply wearing the same protection as for surgical procedures and that none of the staff had come down with covid yet (as of early August, 2020).

      I did notice on the Google document from UCSF that Lambert published the other day that time spent in the presence of a contagious individual seemed to be critical to risk of infection. According to UCSF, 15 to 60 minutes in an enclosed environment with someone who is contagious poses the greatest risk. Other than ERs or ICUs, there aren’t many situations in a hospital where a doctor of nurse spends even 15 minutes with a single patient–too many other patients to see. So maybe that has been, inadvertently, part of the protection in hospital settings.

  6. Rick in Oregon

    Dose to produce infection?

    Seems this should be a part of the answer. Simply stating measles has aerosol spread, therefore produces high transmission compared to covid-19 is simplistic. Perhaps the infectious dose for measles is far lower than for covid-19.

    1. Lambert Strether Post author

      I’m with you on not buying that argument. Different viruses, evolved to do different things! (“It’s airborne so it’s as lethal as measels” just doesn’t strike me as a strong argument._

      1. Reify99

        Asymptomatic spread is another confounding variable. I’ve seen numbers stating that up to 80% of covid-19 cases are asymptomatic. When it’s stated that only 10% of family members get covid from an infected loved one (as compared to 85% of family members catching measles) are they testing the asymptomatic family members?

        I’m with the University of Nebraska. Assume the worst! Stop trying to make the pandemic transactional! Give up on monetizing contact tracing! Man (usually) UP!

        1. Charger01

          The asymptomatic variable is a vexing one. We’re going to keep our 1st grader home due to this fact, unless testing becomes a weekly event.

    2. rd

      Everything I have seen so far indicates that the transmission of covid is about half-way between measles (highly infectious by aerosols) and influenza (moderately infectious by aerosols).. Capps original 1918 paper on masks was focused on measles and scarlet fever and found that patients who were sick wearing masks dramatically reduced transmission of those diseases to other patients in the wards. A June 2018 paper by Capps indicated reduction of scarlet fever transmission of 95% and 100% of measles by wearing masks and following a number of basic hygiene steps similar to what is being recommended by many for Covid today.

      Countries with a high degree of mask wearing today are doing much better than ones that are not. Providing ventilation, filtration, and negative pressure rooms is a substantial additional set of steps reducing risks. the society wide controversy over these measures in the US reminds me of Lilliput and Blefescu being at war with each other over which end of an egg is to be cracked open to to eat it.

  7. Shelby73

    Hospitals will keep lying to save a buck or two. No business interest in this country gives a flying hoot about their employees. WHO is a lying joke for the same reason. MONEY. Also biggest funder of WHO is none other than Bill Gates. I imagine he also controls the narrative to protect his billions and the billions his buddies own.

  8. Brick

    Research from France on an earlier SARS derivative outbreak suggested it was largely spread by droplets however it could hitch a ride on the sneezing from the common cold. Patients with both were more likely to spread the virus. This seems like a common sense idea to me, but then common sense seems to be in short supply. Counter productively many firms have been hit with high sick pay costs are cutting sick pay and encouraging those with colds into work.

    It is interesting how costs are driving the media narrative and the blame game is in full ramp mode. Focus is often on the minority of rule breakers[who should be ashamed] and there is not much empathy for those whose future job prospects ,income and relationships have been trashed. There is very little detail on school virus outbreaks or bad work practices causing outbreaks. I respect that the world economy is fragile and is driving a lot of policy as it should, but I just don’t like being fed biased information.

    I also find it curious that long COVID-19 symptoms is on the peripheral of general awareness particularly since possibly the at most risk demographic for long COVID-19 are those with strong immune systems[younger demographic].The excuse that we are still learning about the virus is starting to wear thin and it looks like the medical profession communication is failing on a multi discipline , region , national and world level.

    Having discussed with friends and family who have caught the virus and how they caught it then I am absolutely certain there is an aerosol element to transmission.

    Stay safe.

    1. GM

      Long COVID is out of the spotlight because someone would have to pay for decades of disability and healthcare costs if it was acknowledged to be a thing.

      1. rd

        It will be a thing pounced on by insurance companies when they can avoid covering pre-existing conditions.

  9. bun

    I’ve yet to see solid data on one crucial piece of knowledge: how MUCH of the SARS-COV-2 virus does one need to ingest before becoming infectious? does anyone here know?

    so it could be ‘airborne’ and last for hours on surfaces, but if one needs a LOT to get infected, then the transmission probability will be low.

    IMO it has to be more than just a little (by some measure) or else we would have been evidence of much higher airborne transmission events rather than comparably few cases like the choir, etc. I think that is where the ‘world of hurt’ and ‘R0 for measles vs cold’ comment come from.

    so it could be ‘airborne’ like measles but not as infectious as measles at the same time, keeping R0 fairly low.
    But these things are NEVER single-valued. Transmission probabilities always follow a distribution – the questions are where the peak or average is (R0), and how long is the tail? (paging Taleb…). So ‘airborne’ transmission can be nonzero, but small, so with enough cases, one will see some airborne cases popping up. this is what it seems to me is happening.

    so to me the questions really is – what is the distribution of how much is needed to get sick ? from this one can get a handle on how much airborne and fomite transmission there could be given the viral loads in any place, such as a hospital, or subway lineup, or whatever. Even if the probability is small, with enough cases the final number can be large enough to really worry about.

    its all about risk mitigation: it really is impossible to bring the risk to zero. its always about bringing it down as much as one can given the constrints. (time, money, resources, etc)

    If anyone has any links to any studies on how much virus it takes to get sick, i’d love to see them.

    1. GM

      Very good point.

      Measles is actually not just airborne, but you only need a few viral particles to contract it — it has an incredibly high affinity for its receptor so you don’t need much at all.

      Also, the R_0 for COVID under conditions of uncontrolled spread and life as usual is not 2.

      This was another point of obfuscation from the very beginning.

      You don’t get the kind of explosion we had in February and March with an R_0 below 2. Which is why if you look at those charts of R_0 over time:

      You will notice how in places like NY even though the plot is cutoff at 2.0, in march the curve actually descends from a much higher value into the plot area. Because it was 3, 4 as much as 5 or 6 perhaps.

      So the whole argument that “R_0 is too low for an airborne virus” is a lie. It is low now because of all the containment measures. Without them it would be very high.

  10. Hayek's Heelbiter

    Broken record here.
    Only solution for BOTH droplets and aerosol.
    Run all the air through a sealed UV-C unit air sanitizer.
    Now I will shut up.

  11. VietnamVet

    US healthcare was privatized and financialized. Managers are unwilling to cut profits to be prudent and save lives. The federal government science agencies are politicalized. Nobody is being jailed for manslaughter. “Nurses of Filipino descent comprise just 4% of the US workforce, but nearly a third of registered nurse deaths due to COVID-19.”

    The US federal government transfers money only to the connected. Spending money to the Main Street businesses to manufacture and supply adequate PPE to save American health worker and patient lives simply isn’t mentioned.

  12. The Rev Kev

    You would think that it would be best to use the precautionary principle here but you don’t hear about that much anymore. The truth of the matter is that if it is spread as an aerosol, then more time, money & resources would have to be spent to deal with that. Cheaper just to pretend that people only have to worry about droplets and ignore the studies about aerosol transmission going back to February then.

    1. Zamfir

      There are different situations here. Hospitals started on the precautionary principle early on, with heavy PPEs, but they have found that mild “droplet” PPEs and protocols work fine. That is not just about cost, heavy PPEs are also stressful to work in. After a while, people keep over from fatigue. It’s not “precautionary” to do that, if you have enough data to know that it is not necessary.

      So for hospitals, the debate is settled. “Droplet” procedures work well, so covid is a “droplet” disease. The actual mechanism involved is, in that light, just angels on a pin debate. They don’t want that to interfere with their work.

      For the world outside of hospitals, the logic is very different. Our here, it’s more relevant to discover to details of the mechanism, because we can’t manage to change the whole outside world to hospital “droplet” procedures.

      That creates a rotten tension. We want the CDC that acknowledge aerosolic spread, to encourage people to think of ways to reduce that spread. But for a hospital, such an acknowledgement is not a nudging bit of information, its a black letter Command. It means, switch to heavy PPEs, right now.

  13. Adam1

    A week or so I read on a link here (or one posted in the comments) about a group of doctors and ventilation engineers who had put together a open google doc about airborne covid-19. One of the amazing things if you go to the google doc is that there is a whole section (1.4) on why there is so much resistance to the discussion of airborne transmission of any virus/disease. It basically boils down to dogma based upon a scientist who believed it might be a technical possibility by lacked any means in 1910 to prove it either way. He also wanted to dispel long held bad ideas about “bad air”. Once quote from his seminal book, “it is impossible, as I know from experience, to teach people to avoid contact infection while they are firmly convinced that the air is the chief vehicle of infection.”

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