Social Distancing is (Almost) Useless

Another early COVID myth has been shattered.

A new study by Martin Z. Bazant and John W. M. Bush of MIT, “A guideline to limit indoor airborne transmission of COVID-19,” is getting quite a bit of attention. Rather than regurgitate breathless press accounts, I’m going to reproduce the abstract:


Airborne transmission arises through the inhalation of aerosol droplets exhaled by an infected person and is now thought to be the primary transmission route of COVID-19. By assuming that the respiratory droplets are mixed uniformly through an indoor space, we derive a simple safety guideline for mitigating airborne transmission that would impose an upper bound on the product of the number of occupants and their time spent in a room. Our theoretical model quantifies the extent to which transmission risk is reduced in large rooms with high air exchange rates, increased for more vigorous respiratory activities, and dramatically reduced by the use of face masks. Consideration of a number of outbreaks yields self-consistent estimates for the infectiousness of the new coronavirus.


The current revival of the American economy is being predicated on social distancing, specifically the Six-Foot Rule, a guideline that offers little protection from pathogen-bearing aerosol droplets sufficiently small to be continuously mixed through an indoor space. The importance of airborne transmission of COVID-19 is now widely recognized. While tools for risk assessment have recently been developed, no safety guideline has been proposed to protect against it. We here build on models of airborne disease transmission in order to derive an indoor safety guideline that would impose an upper bound on the “cumulative exposure time,” the product of the number of occupants and their time in an enclosed space. We demonstrate how this bound depends on the rates of ventilation and air filtration, dimensions of the room, breathing rate, respiratory activity and face mask use of its occupants, and infectiousness of the respiratory aerosols. By synthesizing available data from the best-characterized indoor spreading events with respiratory drop size distributions, we estimate an infectious dose on the order of 10 aerosol-borne virions. The new virus (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) is thus inferred to be an order of magnitude more infectious than its forerunner (SARS-CoV), consistent with the pandemic status achieved by COVID-19. Case studies are presented for classrooms and nursing homes, and a spreadsheet and online app are provided to facilitate use of our guideline. Implications for contact tracing and quarantining are considered, and appropriate caveats enumerated. Particular consideration is given to respiratory jets, which may substantially elevate risk when face masks are not worn.

COVID-19 is an infectious pneumonia that appeared in Wuhan, Hubei Province, China, in December 2019 and has since caused a global pandemic (1, 2). The pathogen responsible for COVID-19, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is known to be transported by respiratory droplets exhaled by an infected person (3⇓⇓⇓-7). There are thought to be three possible routes of human-to-human transmission of COVID-19: large drop transmission from the mouth of an infected person to the mouth, nose or eyes of the recipient; physical contact with droplets deposited on surfaces (fomites) and subsequent transfer to the recipient’s respiratory mucosae; and inhalation of the microdroplets ejected by an infected person and held aloft by ambient air currents (6, 8). We subsequently refer to these three modes of transmission as, respectively, “large-drop,” “contact,” and “airborne” transmission, while noting that the distinction between large-drop and airborne transmission is somewhat nebulous given the continuum of sizes of emitted droplets (11).* We here build upon the existing theoretical framework for describing airborne disease transmission (12⇓⇓⇓⇓⇓-18) in order to characterize the evolution of the concentration of pathogen-laden droplets in a well-mixed room, and the associated risk of infection to its occupants.

The Six-Foot Rule is a social distancing recommendation by the US Centers for Disease Control and Prevention, based on the assumption that the primary vector of pathogen transmission is the large drops ejected from the most vigorous exhalation events, coughing and sneezing (5, 19). Indeed, high-speed visualization of such events reveals that 6 ft corresponds roughly to the maximum range of the largest, millimeter-scale drops (20). Compliance to the Six-Foot Rule will thus substantially reduce the risk of such large-drop transmission. However, the liquid drops expelled by respiratory events are known to span a considerable range of scales, with radii varying from fractions of a micron to millimeters (11, 21).

There is now overwhelming evidence that indoor airborne transmission associated with relatively small, micron-scale aerosol droplets plays a dominant role in the spread of COVID-19 (4, 5, 7, 17⇓-19, 22), especially for so-called “superspreading events” (25⇓⇓-28), which invariably occur indoors (29). For example, at the 2.5-h-long Skagit Valley Chorale choir practice that took place in Washington State on March 10, some 53 of 61 attendees were infected, presumably not all of them within 6 ft of the initially infected individual (25). Similarly, when 23 of 68 passengers were infected on a 2-h bus journey in Ningbo, China, their seated locations were uncorrelated with distance to the index case (28). Airborne transmission was also implicated in the COVID-19 outbreak between residents of a Korean high-rise building whose apartments were linked via air ducts (30). Studies have also confirmed the presence of infectious SARS-CoV-2 virions in respiratory aerosols (31) suspended in air samples collected at distances as large as 16 ft from infected patients in a hospital room (3). Further evidence for the dominance of indoor airborne transmission has come from an analysis of 7,324 early cases outside the Hubei Province, in 320 cities across mainland China (32). The authors found that all clusters of three or more cases occurred indoors, 80% arising inside apartment homes and 34% potentially involving public transportation; only a single transmission was recorded outdoors. Finally, the fact that face mask directives have been more effective than either lockdowns or social distancing in controlling the spread of COVID-19 (22, 33) is consistent with indoor airborne transmission as the primary driver of the global pandemic.

The theoretical model developed herein informs the risk of airborne transmission resulting from the inhalation of small, aerosol droplets that remain suspended for extended periods within closed, well-mixed indoor spaces. When people cough, sneeze, sing, speak, or breathe, they expel an array of liquid droplets formed by the shear-induced or capillary destabilization of the mucosal linings of the lungs and respiratory tract (8, 34, 35) and saliva in the mouth (36, 37). When the person is infectious, these droplets of sputum are potentially pathogen bearing, and represent the principle vector of disease transmission. The range of the exhaled pathogens is determined by the radii of the carrier droplets, which typically lie in the range of 0.1 μm to 1 mm. While the majority are submicron in scale, the drop size distribution depends on the form of exhalation event (11). For normal breathing, the drop radii vary between 0.1 and 5.0 μm, with a peak around 0.5 μm (11, 38, 39). Relatively large drops are more prevalent in the case of more violent expiratory events such as coughing and sneezing (20, 40). The ultimate fate of the droplets is determined by their size and the airflows they encounter (41, 42). Exhalation events are accompanied by a time-dependent gas-phase flow emitted from the mouth that may be roughly characterized in terms of either continuous turbulent jets or discrete puffs (20, 38, 43). The precise form of the gas flow depends on the nature of the exhalation event, specifically the time dependence of the flux of air expelled. Coughs and sneezes result in violent, episodic puff releases (20), while speaking and singing result in a puff train that may be well approximated as a continuous turbulent jet (38, 43). Eventually, the small droplets settle out of such turbulent gas flows. In the presence of a quiescent ambient, they then settle to the floor; however, in the well-mixed ambient more typical of a ventilated space, sufficiently small drops may be suspended by the ambient airflow and mixed throughout the room until being removed by the ventilation outflow or inhaled (SI Appendix, section 1).

Theoretical models of airborne disease transmission in closed, well-mixed spaces are based on the seminal work of Wells (44) and Riley et al. (45), and have been applied to describe the spread of airborne pathogens including tuberculosis, measles, influenza, H1N1, coronavirus (SARS-CoV) (12⇓⇓⇓-16, 46, 47), and, most recently, the novel coronavirus (SARS-CoV-2) (17, 25). These models are all based on the premise that the space of interest is well mixed; thus, the pathogen is distributed uniformly throughout. In such well-mixed spaces, one is no safer from airborne pathogens at 60 ft than 6 ft. The Wells-Riley model (13, 15) highlights the role of the room’s ventilation outflow rate Q in the rate of infection, showing that the transmission rate is inversely proportional to Q, a trend supported by data on the spreading of airborne respiratory diseases on college campuses (48). The additional effects of viral deactivation, sedimentation dynamics, and the polydispersity of the suspended droplets were considered by Nicas et al. (14) and Stilianakis and Drossinos (16). The equations describing pathogen transport in well-mixed, closed spaces are thus well established and have recently been applied to provide risk assessments for indoor airborne COVID-19 transmission (17, 18). We use a similar mathematical framework here in order to derive a simple safety guideline.

We begin by describing the dynamics of airborne pathogen in a well-mixed room, on the basis of which we deduce an estimate for the rate of inhalation of pathogen by its occupants. We proceed by deducing the associated infection rate from a single infected individual to a susceptible person. We illustrate how the model’s epidemiological parameter, a measure of the infectiousness of COVID-19, may be estimated from available epidemiological data, including transmission rates in a number of spreading events, and expiratory drop size distributions (11). Our estimates for this parameter are consistent with the pandemic status of COVID-19 in that they exceed those of SARS-CoV (17); however, our study calls for refined estimates through consideration of more such field data. Most importantly, our study yields a safety guideline for mitigating airborne transmission via limitation of indoor occupancy and exposure time, a guideline that allows for a simple quantitative assessment of risk in various settings. Finally, we consider the additional risk associated with respiratory jets, which may be considerable when face masks are not being worn.

I haven’t had time, and will likely not take time, to read the entire paper, which is available both inline and in PDF format, at the link. Frankly, my mathematical literacy is likely insufficient to glean more from the full paper than the abstract.

But, based on my lay understanding of the findings, it seems that:

  • “Six feet” is a meaningless number with respect to this disease. Short contact at three feet is likely no more dangerous and prolonged exposure at sixty feet is almost certainly more dangerous than limited exposure at six feet.
  • But it’s not true to say that distancing doesn’t matter. It’s just far less important than duration, ventilation, and exposure time.
  • Clearly, what people are doing in the space matters as well. Ordinary breathing is less of a spreading event than heavy breathing or singing. Duh.
  • Further, wearing a decent faskmask (and, obviously, getting vaccinated, not considered in the study given the timelines involved) matters a hell of a lot more than distance, at least in the context of a relatively confined space like a restaurant or a church.
  • Frustratingly, though, public health officials, responding to guidelines from CDC, WHO, and others who have access to the modeling, are still regulating based on the state of our knowledge about the disease—which was quite reasonably extrapolated from what we knew about SARS, H1N1, and previous pandemics—a year ago.

Some things to keep in mind:

  • Neither of the co-authors are physicians or epidemiologists.
  • Still, they have impressive credentials. Bazant has his PhD in physics from Harvard but has dual appointments in the chemical engineering and mathematics departments at MIT. Bush has his PhD in geophysics from Harvard, has an appointment in the mathematics department at MIT, and his recent work deals with “surface tension-driven phenomena and their applications in biology.” The reviewer was Cal Tech’s John H. Seinfeld, a very senior scholar whose work focuses on “Atmospheric chemistry and physics, Aerosols.”
  • This work is mostly theoretical—based on modeling and computer simulations—but informed by how the disease has performed in the wild, particularly in “superspreader” events.

That said, the findings comport with what we already know from the observational evidence. Most obviously, restaurants, where most states that have allowed indoor dining to resume have done so with physical distancing requirements, have been far and away the biggest contributor to outbreaks. And this is because, while the guidelines typically require tables be arranged such that diners not of the same party are at least 6 feet apart, most patrons take off their masks while seated and leave them off for the duration of their stay. Meanwhile, truly outdoor dining (as contrasted with mostly enclosed tents that have poor circulation) has not at all been linked to disease spread.

UPDATE: Bruce Y. Lee, who among other things is a Professor of Health Policy and Management at the City University of New York (CUNY), offers some further cautions about reading too much into the study. Most directly, he’s confronting those in right-wing media who are claiming that the study says that we should stop social distancing and masking, which clearly isn’t what it says. But, also, he objects to the study’s focus on microparticulates in a “well-mixed room,” noting there are other possible vectors.

Remember the study did miss a big thing. Or at least a bigger thing or a bunch of bigger things: the larger respiratory droplets that can come out of a person’s mouth. It also missed the even bigger things that may be spewing out the respiratory droplets and touching you, touching me: people. The six foot distance is to keep people from directly contacting each other and the larger respiratory droplets from their mouths from reaching other people.

As you probably have observed, people don’t usually talk to each other standing straight with their arms glued to their sides, looking like Lego people. Instead, they often gesticulate, waving their hands and arms as if they were throwing cabbage at others, getting Bruno Mars to sit at their table, or both at the same time. A six foot or one Denzel radius can help prevent accidental contact, you know, the “sorry, was that your face that my hand hit” type of contact.

Such a radius can also keep you clear of the rotating spit sprinklers that people tend to be.

While I think this overstates things (I believe, intentionally as an attention-getting device) it’s certainly reasonable. But, again, I think he’s reacting to people intentionally misreading the study, not the study itself.

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James Joyner
About James Joyner
James Joyner is Professor and Department Head of Security Studies at Marine Corps University's Command and Staff College. He's a former Army officer and Desert Storm veteran. Views expressed here are his own. Follow James on Twitter @DrJJoyner.


  1. MarkedMan says:

    The public only occasionally gets exposed to scientific sausage making. This is one study based on a model. It may hold up as others weigh in using other methods, or it may turn out that the model was deficient in some aspects. Officials are correct not to change advice based on this one paper.

  2. James Joyner says:

    @MarkedMan: Oh, absolutely. But there are other papers showing the same things.

    I don’t see the takeaway as “keeping one’s distance is a bad idea” but rather “keeping 6 feet isn’t likely to help all that much” if you’re maskless in a relatively confined space.

  3. Jen says:

    As an introvert who enjoys my personal space, I’m going to choose to ignore this study. If conservatives can ignore all of the other science, I’m going to keep to the one aspect of this pandemic that has worked well for me. 😀

    Seriously though, the droplets issue is a big one–there are some people who are simply more apt to talk a lot, often, with projection and it’s almost a certainty that being in close proximity to such an individual who is infected could present a viral load issue.

  4. MarkedMan says:

    FWIW, this once again calls into question the efficacy of cloth masks. If transmission is via aerosol then a cloth mask does little to block that. As far as I know there is no study that answers this question in a meaningful way, and we’ve* been wearing them for over a year.

    *“We”, in his case, is collective. Early on I got N95’s for me and my family.

  5. SKI says:

    @MarkedMan: Not correct. A cloth barrier is not impermeable but does drastically reduce the “jet effect” that extends the range of the transmission.

  6. Not the IT Dept. says:

    I think you should change the subheading on this post; one study does not strike me as sufficient to suggest it’s “shattering” anything. Also, let’s err on the side of caution; unless social distancing is dangerous, there’s no reason not to do it until further evidence is available.

  7. steve says:

    Transmission can be either by aerosol or by droplet. Cloth masks reduce droplets and if you look at the laser studies they probably decrease the aerosol a bit. If you look at the animal studies where they put caged hamsters (pretty sure it was hamsters) in separate cages with and without masking material between them what you found is both a lower rate of infection when you have mask material but those who got infected were not as sick. I would interpret that as aerosols still being able to get past the mask stuff but not droplets so that there was less of a viral load. So masks that cannot stop aerosol transmission may still help.

    As to the study I think what it shows is that the time factor is important. The longer you are in a confined space, especially with poor ventilation, the more that distancing does not matter. If you engage in activities that put more virus into the air, like singing, the less distancing matters. I would think that 3 feet is still worse than 6 feet just because you would be in range of larger droplets which would influence not only the likelihood of transmission but also the severity of illness. So I would say this study tells us that for most daily activities the 6 foot rule is still good, especially if you mask. Avoid large groups of people in confined spaces unless it is time limited, especially if they are singing, yelling, etc.


  8. Scott says:

    My technically illiterate far right congressman, Chip Roy, totally misread and misquoted this study and basically indicated the last year of social distancing and mask wearing was a waste. In response, every respondent told him to actually read and understand the article.

    There are going to be a lot more studies, most of which should just stay in the scientific community because they will be misused.

    Personally, my pet uninformed theory is that the outbreak last summer in the South was the result of everyone retreating into the air-conditioning. This study does lend support to that idea.

  9. Long Time Listener says:

    Trying looking through the windshield, on a drive into the afternoon sun, whilst talking on a hands-free device. The amount of particle-spray that I can see coming from just speaking is enough to make me pro-mask/pro-distancing.

  10. Scott F. says:

    Clearly, what people are doing in the space matters as well. Ordinary breathing is less of a spreading event than heavy breathing or singing. Duh.

    …Or pontificating at the end of a bar or talking across a table at a noisy restaurant.

    This study supports the lockdown logic as I‘ve understood it from nearly the beginning. Passing through a store to shop is much less risky than lingering in a restaurant or bar. A few hours in a crowded theater or church or political rally is more dangerous than a few minutes in a crowd on the street. This wasn‘t so complicated until it was dumbed down and made political.

  11. James Joyner says:

    @Not the IT Dept.:

    unless social distancing is dangerous, there’s no reason not to do it until further evidence is available.

    Sure. But I think the takeaway isn’t that the inconvenience of being six feet apart is silly but that being six feet apart doesn’t protect you all that much from aerosolized droplets in a relatively confined space that recirculates the air.

  12. mattbernius says:

    One by-product of social distancing is it effectively reduces the number of people who are able to be served inside a restaurant at a given time due to the need to distance tables. That most likely helped limit the spread as well.

    So this could be a case of getting it right, albeit for potentially not the correct reason. This actually happens a lot more often in the development of science than many people care to admit.

  13. Tim says:

    @James@James Joyner:

    I may be nitpicking, but I really think the word “myth” in your sub-heading is misleading. It wasn’t a myth for public health experts to take what information they had about the virus early on, and based upon years of experience, make common-sense recommendations regarding social distancing and mask wearing. The word “myth” should be reserved for fantasies like the kind of crap the anti-vaxxers continuously throw around.

  14. Tim says:

    @James Joyner:

    I may be nitpicking, but I really think the word “myth” in your sub-heading is misleading. It wasn’t a myth for public health experts to take what information they had about the virus early on, and based upon years of experience, make common-sense recommendations regarding social distancing and mask wearing. The word “myth” should be reserved for fantasies like the kind of crap the anti-vaxxers continuously throw around.

  15. OzarkHillbilly says:

    Social Distancing is (Almost) Useless

    I just gotta say that in my experience it has been most useful. It certainly has reduced my homicidal urges.

  16. Kathy says:

    I’ll say for the Nth time there is no single 100% way of stopping the spread of COVID and there never will be. This doesn’t mean all the means for reduction available like masks, distancing, good hygiene, etc. don’t add up to fewer cases, fewer deaths, and fewer long-term consequences.

  17. MarkedMan says:

    @SKI: The jet effect refers to droplets, which fall out of the air within a few seconds. If the viral transmission is via aerosol, well, the virus is 100nm in diameter and basically doesn’t give a hoot about gravity. It will stay suspended nearly indefinitely. So it doesn’t matter if it takes a few minutes to reach you, it’s not going to fall out of the air before it does.

  18. MarkedMan says:

    @steve: I assume you mean this study? It was done with surgical mask material and not cloth masks. Surgical masks have one or two layers of actual filter material as well as a vapor barrier that prevents seepage of liquid from one side to the other. While not nearly as effective as a close fitting N95 at stopping viral transmission they should be better, perhaps significantly better, than a cloth mask.

    I agree that we don’t know how effective cloth masks are, for a bunch of reasons. But I would strongly encourage everyone to spend a few dollars and get an N95 or KN95 mask. They can be reused for weeks or months with little degradation in filtering capability and they are now readily available. And they most certainly stop 95% or more of aerosol particles the size of the virus. I have tested some of them myself.

  19. Jim Brown 32 says:

    If we stopped using Flu/Cold as the baseline of transmission models–and instead used Tuberculosis. We’d be at the 80% solution.

  20. drj says:

    @James Joyner:

    But I think the takeaway isn’t that the inconvenience of being six feet apart is silly but that being six feet apart doesn’t protect you all that much from aerosolized droplets in a relatively confined space that recirculates the air.

    Of course. But the goal of public health measures such as these is not transmission impossible but to make such transmissions harder.

    This isn’t about keeping individuals safe (as one would try to do with, e.g., hospital staff) but to limit spread and/or infection rates among an entire population (which simply cannot be protected to the same degree).

    You’re coming at this from the wrong perspective.

    This isn’t about you or me, this is about millions of us.

  21. Michael Reynolds says:

    People with severe intellectual limits (tryin’ to clean up my language) need simple, concrete answers. Not true answers, mind you, but simple and unchanging answers even in the face of new evidence. See: religion.

    People with fewer intellectual limits understand that it can take a minute to get all the facts surrounding a new challenge. See: science.

  22. drj says:

    ETA: And thus the question becomes whether social distancing is a useful tool (among other tools) to keep infection rates down, rather than to keep everyone who practices social distancing safe.

    Social distancing was never meant to the one single bullet that would keep everyone safe. This means that even if it would cut infection rates by a mere 5%, it could still be very much worth it.

    After all, we are dealing, potentially, with an exponential growth in infection rates.

  23. drj says:

    @Michael Reynolds:

    People with severe intellectual limits (tryin’ to clean up my language) need simple, concrete answers.

    It’s not even just that. In situations such as these, there need to be rules that are simple and unambiguous.

    “Stay six feet apart,” is workable. “Stay three feet apart if the interaction lasts less than one minute, but twelve feet if it lasts for ten minutes,” isn’t.

  24. James Joyner says:

    @Tim: I acknowledge that in the OP. I use “myth” here because, as with the perfectly reasonable starting-off belief that maniacally disinfecting surfaces was useful, the “6 feet apart” thing has stuck with us long after the empirical evidence demonstrated otherwise.

  25. Teve says:

    @drj: I do sous vide cooking that my Trumper relatives refuse to eat. They insist that if it didn’t hit 165 F it’s the foulest poison. I tried, once, carefully, to explain about how it’s not just temperature, it’s time and temperature. I used analogies. I referenced the national microbiology license I got 20 years ago to be a hospital lab tech. I pointed out that the USDA and FDA have approved sous vide for restaurants.

    After all that their response was to email me an FDA pamphlet saying 165 F.

    And as you know that’s why you want the FDA making simple, idiot-proof guides. You don’t want people like this trying to work out bacterial survival rates for campylobacter from lin/log charts. Just tell them 165 F and let’s get to the bar. 😀

  26. Cheryl Rofer says:

    Late to the thread, and others have said some of this, but I must reiterate:


    Don’t feel you can understand this stuff fully if you’re not an epidemiologist or other specialist, for whom the paper is intended.

    Don’t cherry pick a single study because it agrees with your priors.

    And, most of all, Don’t share your half-baked and probably prejudicial thinking by putting it on a blog.

    Wait and see what the experts say.

  27. James Joyner says:

    @Teve: Ha. I’ve been on the sous vide bandwagon for a number of years. I tend to do beef to 130 and pork and chicken to 160. (I also love it as a defrosting tool. At 100, it’ll defrost a huge chunk of ground beef in like half an hour and it’ll still be nice and red, rather than turning gray like microwave defrosting.)

  28. Teve says:

    @James Joyner: I’ll do chicken at 140 and beef and pork at the medium rare 135, but I wouldn’t go below 130. (For the final cook, not the defrosting you mention.) some people will cook things at 120 and I’d be a little hesitant about that.

    here is a great recipe for glazed carrots at 183 they’re terrific.

  29. Kingdaddy says:

    I have to pile on here. No “myth” was “shattered.” A couple of scientists, who may be experts in how aerosolized particles travel, but not in disease transmission, published a model. It’s an interesting way of framing the way we talk about COVID-19 transmission, but its hardly definitive. Of course, anyone saying that it shatters myths is encouraging exactly the sort of unintentional or willful misreading of the study.

    Even if this model proves to be the best one any scientist has developed, it’s still not an argument against social distancing. Go back and watch the infamous Rose Garden ceremony that turned into a super-spreader event. The problem isn’t that they weren’t behaving like statues that were placed too close together. They were leaning in to talk to each other, hugging, and doing lots of other understandably human things that happen when you don’t place an invisible fence between people. Even though they were outside, those behaviors increased the risk of transmission.

  30. gVOR08 says:

    @Scott F.:

    Passing through a store to shop is much less risky than lingering in a restaurant or bar. A few hours in a crowded theater or church or political rally is more dangerous than a few minutes in a crowd on the street.

    I realize it’s a very low bar, but that statement shows you’re smarter than the average conservative Supreme Court Justice.

  31. Teve says:

    I’ve got some raw shrimp in the freezer that I’m going to do at 135 with butter, smoked paprika, and tons of garlic, and they’re terrific like that.

  32. Kingdaddy says:

    @Michael Reynolds: Even the smartest people benefit from simpler rules. Not everyone has the time to research the different risk scenarios, and how to mitigate each of them.

  33. Andre Kenji de Sousa says:

    The research seems to point out that sanitizers are useless, not social distance per se. People emit aerosols that can transmit the disease, so, it definitely helps.

  34. Kathy says:

    in simple terms, people are the source of COVID infection. Therefore, it makes sense to avoid people. When this is not possible, like right now that I’m at the office, the next best thing is for everyone to wear masks and keep their distance.

    Since about half won’t wear masks consistently, nor keep their distance, all I’ve got left is to wear a KN95 mask and hope it will keep their SARS-CoV-2 away.

    Thus far just at our department we’ve had, five COVID cases. One required days at the ICU, and all recovered. I don’t assume these people are either immune (though that’s their problem) or cannot transmit COVID anymore, just that the odds are lower. A grand total of two have been vaccinated, one after their return from the ICU, and only one has had both doses.

  35. Michael Reynolds says:

    As to rules, I agree completely. I wear a mask outdoors knowing perfectly well that it’s essentially irrelevant, pour encourager les autres, because we need to keep it simple. But we need to keep it simple for simple people. People a bit quicker on the uptake could re-program.

    The same sort of thing for vaccinations – I opposed all complex schemes. Shots in arms as fast as possible. If you want to add one complicating criterion: age. Other than that, just push the fucking vaccine into arms, any arm, every arm.

  36. gVOR08 says:

    Whatever this and other studies say, being next to a potentially infectious person seems like a good thing to avoid.

  37. just nutha says:

    @Andre Kenji de Sousa:

    sanitizers are useless,

    I wish we’d get out of the habit of using terms such as “useless” when what we really mean is “not of primary importance.” Just sayin’…

  38. Michael Reynolds says:

    This just in: CDC says vaccinated people no longer need to wear masks outdoors.

    Give that a couple days to percolate and no one will be masking outdoors.

  39. just nutha says:

    @Michael Reynolds: And I normally don’t outdoors because in my neighborhood, I encounter one of “les autres” for about every 8-10 hours of walking. When I cross the river to walk at the lake, where I encounter un autre about every 5o or so feet, yeah, I wear a mask. (Or smoke a cigar. They are very effective social distancing tools. 😉 )

  40. Andre Kenji de Sousa says:

    @just nutha: For Covid sanitizers are basically useless, surface to surface doesn’t seem to exist.

  41. MarkedMan says:

    @Andre Kenji de Sousa:

    People emit aerosols that can transmit the disease, so, it definitely helps.

    I think a lot of people get confused by what is meant by aerosols in this case, probably because we associate it with things like “aerosol” deodorants. Large particles such as droplets, which are greater than (and this depends on who’s defining it) 2 – 10 microns, don’t stay in the air very long, typically a few seconds or less. For droplets, even fine droplets, cloth masks probably make a big difference, as does physical distancing.

    On the other hand, aerosols are so small that gravity has little affect on them compared to the forces from the air around them, and so they can stay suspended in the air for hours or days. As an example, a coworker creates an aerosol mixture by taking a basketball, injecting the tiny particles (<1 micron) and then bouncing the ball for a minute or so. He then uses a needle valve and the pressure in the basketball to inject a small amount into an airstream to be sampled. He can let that ball sit on the floor, then come back to that it the next day and it hasn't significantly settled out.

    If transmission is mostly via droplets you could stand two people at opposite ends of a room 10 feet long and 3 feet wide and the transmission risk would be low. On the other hand, if transmission is mostly via aerosols within 15-20 minutes the entire room would be suffused with particles and it wouldn't matter where you stand.

  42. MarkedMan says:

    @just nutha: Yep. And for other types of diseases, sanitizers might be very effective. So maybe, “Not of primary importance in this case.”

  43. Andy says:

    I’m skeptical of modeling studies generally, but this seems to align with studies going back to last summer as well as common sense. So it’s not just one study, it’s just the latest in a series of studies. I recall one from last summer that examined how prison guards with full PPE masks were getting covid despite social distancing and only intermittent direct contact with prisoners.

    So yes, the 6ft rule is arbitrary and doesn’t consider other factors. Yes, there are lots of annoying little Karens who will stupidly yell at you if you are 5 feet away because they think 6ft is some kind of force field. Same with masks. There are still people who are living in March 2020 who will yell at you if you don’t have a mask on outdoors. And of course, there are plenty of people who are willing to bend or ignore the rules when it’s politically convenient.

    However, I think most normal people (who have a bit of introspection and aren’t filled with the self-righteous need to scold anyone who doesn’t share their risk profile) understand that the “rules” are kind like the Pirates Code and are more like guidelines or rules of thumb than dogma.

    I’ll continue to follow my own risk profile while minding the developed social norms in my local area which means only mask outdoors if you’re in very close proximity to someone, always mask indoors, and make a good-faith effort to give people space in public places, indoors or out.

    I doubt it will happen, but I’m hoping the CDC and others learn something about public messaging from this and stop pushing false precision and the noble lie.

  44. Jen says:

    @Andy: I’m sure it was unintentional, but your post comes across as a wee bit condescending. This bit in particular:

    However, I think most normal people (who have a bit of introspection and aren’t filled with the self-righteous need to scold anyone who doesn’t share their risk profile)

    Bottom line: when you’re out in public, you don’t have any idea what any individual’s risk profile is. That healthy looking young person could be a cancer patient (one of my best friends had breast cancer at age 35), or a transplant recipient. The “outside is okay” is stretching it too–outside when there’s plenty of open space is far different than outside in a crowded downtown area.

    I’m tiny and am certainly not going to pick a fight with someone, but I do want people to stay the eff away from me, especially the ones who haven’t yet digested that their noses are part of their respiratory system. And when I’m in line and the floor is nothing but 12″x 12″ linoleum tiles, I’d better be able to count six between me and the next guy.

    CDC is doing the best they can. Messaging complex rules with changing parameters is HARD. I say this as a professional communicator.

  45. David S. says:

    It’s always fascinating to see people justify their anti-health positions. It’s never a list of citations; it’s always “that one study”. And it’s never “I agree with the authors of the study, having challenged their methodology and finding it holds up,” it’s “I’m so much bolder than the authors of the study that I am willing to draw conclusions they weren’t”.

    @Andy: You know that wearing a mask has nothing to do with protecting yourself, right? Like, telling Americans that it protects them is the only way to get them to wear a mask, sure, but that’s never been why the public is supposed to wear them.

    The purpose of a mask is to stop the virus from transmitting *from the wearer* to someone else. Your risk profile is incredibly irrelevant to whether or not you should mask up. The fact that it also makes the wearer less likely to get infected is a happy side effect.

  46. Andy says:


    Bottom line: when you’re out in public, you don’t have any idea what any individual’s risk profile is.

    Yes, that’s the point. Because one doesn’t know others’ risk profiles, it is unreasonable to expect that everyone else should adhere to mine or yours. If one chooses to take the risk to go out in public, one cannot demand that the public act in accordance with your personal wishes or comfort level, which is what the self-righteous scolds do.

    And when I’m in line and the floor is nothing but 12″x 12″ linoleum tiles, I’d better be able to count six between me and the next guy.

    I doubt very much that most people are counting tiles. Certainly, I’ve never done that – I always ballpark the distance because I realize the 6ft is arbitrary and a foot one way or the other doesn’t make any difference.

    But if the difference between 5ft and 6ft is really that important to you, then you should at least be nice about it when you ask them to back up or give you more space and not assume they should be counting tiles or instinctively accommodating your personal risk profile.

    CDC is doing the best they can. Messaging complex rules with changing parameters is HARD.

    Sure messaging is hard but most experts agree that they failed in many respects, even according to their own criteria. There are lessons that need to be learned.

    @David S.:

    You know that wearing a mask has nothing to do with protecting yourself, right?

    Yes, I know that. I also know that masking outdoors is not necessary unless I’m in close proximity to others. In fact, we knew that last summer.

  47. Michael Reynolds says:

    I tend to harp on epistemology – how and why people know what they know – because the root cause of the problem is that people don’t know how they know what they know and as a result what they know is often bullshit. If you don’t know how to differentiate between opinion and fact you elect Donald Trump and think Bill Gates is putting microchips in vaccines.

    A solution might be to start teaching some philosophy far earlier than college. We could teach people how to tell opinion or guesswork from fact. But we can’t do that, because that critical ability is the seed of atheism.

  48. Kathy says:

    @Michael Reynolds:

    I took two semesters of philosophy in high school. I hated it. It seemed like an endless parade of opinions by men long dead who knew far less about the world than I did.

    I grant you the teachers were a huge problem. Pretty much you had to memorize what Democritus said about atoms or Plato about forms, and then regurgitate it come test time. We learned little abut the methodology, and there were zero discussions about the principles involved (and shouldn’t that be the whole point?)

    I got my habit of critical thinking from chemistry and physics in junior high school, plus first watching Sagan’s “Cosmos” and then reading extensively about science. Narrative and internal consistency is not enough to pass for science.

    There’s a joke that a university president is taking the physics department to task for their outrageous budget requests.

    “Cyclotrons!” the president says angrily. “Lasers! Refined materials! What do you need all that for? Look at the math department, all they want are pencils and erasers. Or the philosophy department. they don’t even need erasers!”

  49. James Joyner says:

    @Kathy: Making judgments about an academic discipline based on how it’s taught it high school is dangerous. History is fantastic in college; in high school it’s about memorizing dates.

    On my first day teaching the Intro to American Governments class, I would always asked students to raise their hand if they had the subject in high school. Most had, in 11th grade. Next, I asked how many of their teachers for the class had the first name ‘Coach.’ Almost all the same folks.

    Okay, we’ll start from the beginning then.

  50. Kathy says:

    @James Joyner:

    Making judgments about an academic discipline based on how it’s taught it high school is dangerous.

    Maybe so. but high school students new to a subject are ignorant of it. What and how they are taught it, will determine what they judge the subject to be.

    History is fantastic in college; in high school it’s about memorizing dates.

    Case in point. I’ve mentioned my junior high school history teacher a number of times. She was amazing, and she never asked for a single date in a test. We went into antecedents, causes, politics, motivations, economics, etc.

  51. Just nutha ignint cracker says:

    @MarkedMan: I’m pretty confident that if either you or Andre Kenji realized that I often forget and cough/sneeze into the handkerchief that I use to blow my nose, that you both would rather that I’ve used useless/not of primary importance hand sanitizer before I shake hands with you. Context is everything.

  52. Andy says:

    @Michael Reynolds:

    You’re exactly right that people don’t know how they know what they know – most often they rely on third parties.

    My kid’s high school offers a “theory of knowledge” course for juniors which I encouraged them to take. Given the media saturation, I think such courses, as well as philosophy, are critical subjects for a modern curriculum. It at least provides some route for introspection which is more important than ever IMO.

    The part I disagree with you about is that critical thinking is the seed of atheism. IMO it’s the seed of agnosticism. Atheism is just a secular religion, as self-assured in its precepts as any other. We’re hard-wired for faith-based thinking and the absence of a formal religion doesn’t change that.

  53. Grewgills says:


    Atheism is just a secular religion

    That demonstrates a fundamental misunderstanding of what atheism is.
    Almost everyone is atheist about almost every god.
    People aren’t generally agnostic about Thor, or Zeus, or Osiris.
    Atheists equally don’t believe in gods as they don’t believe in unicorns or fairies.
    Not believing in fairies because there is not evidence of fairies is no more a religion than not believing in gods.
    Honest question, are you agnostic about the existence of fairies or unicorns?

  54. Kathy says:


    You know, Rome fell after the Romans discarded the religion of their ancestors and adopted Christianity.


    Maybe Minerva, Juno, Jupiter, Mars, Neptune, et. al. were so pissed at this snub, they withdrew the favor they’d shown old Rome.

    there are scholars who deem Christianity as one factor, or the main factor, in Rome’s decline. but none claim it was revenge by the Olympian gods.

  55. grumpy realist says:

    @Kathy: As a pagan, my suspicion is that the gods got bored….
    (Difficult being a devotee of a religion where you have the constant suspicion that the only reason your deities interact with you is because you’re a lab rat in some ineffable game of theirs. There’s a reason I try to deal with them as little as possible.)