Is it the primary mode or do both droplets and aerosols transmit it? I thought we started with droplets and surfaces and crossed off surfaces and added aerosols.
That article seems to make the same category mistake you are, by characterizing masks as either working or not.
That article simply collects facts about masks, but had almost nothing about how their behavior might interfere with the real process of the spread of vivid.
It reminds me a little (if memory serves) of some aids scare tactics back in the 90s. The claim was that the hiv virus could easily fit between the pores in a latex condom. Never mind that (I guess) hiv must be in a white blood cell or similar to be transmitted during sex, and this does not fit through.
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āweā?
For a ānovelā virus, why didnāt āweā include aerosols in the initial possibility set? Seems foolish, especially given how many other respiratory viruses spread through aerosols.
āweā (which is really WHO) didnāt include aerosols initially, largely for political reasons. If they had admitted it might be spread by aerosols they would have also had to recommend that medical personnel who treated patients with covid had to had access to respirators and other expensive equipment, and the WHO didnāt want to piss off a lot of poor countries that couldnāt afford to do that by actually acknowledging the fact.
But @magillaG is correct that āmasks work, true or falseā is the wrong question. I have previously pointed you to careful mathematical models showing that how much masks work depends on the percent of virus they capture (which is always less than 100%), how many viral particles it typically takes to infect a person, how many people are in what volume of air, and how often that air turns over. And under a wide range of reasonable, fact-based answers to those questions (pre-delta) even crappy cotton masks that stop about 30% of virions from passing through them reduced the risk of a kid catching covid in a classroom by an enormous fraction. Surgical masks are even better. And of course, respirators work very well.
Now, i have been wondering if the vastly higher viral load produced by delta overturns those results. And i havenāt seen any updates, yet. In my social circles we have upgraded to āsurgical masks or betterā when we get together in person.
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Thatās interestingā¦ Iād never heard that before.
I wish theyād freaking be plain. Thereās nothing wrong with saying āmay or may not be spread by aerosolsā if you truly donāt know.
Communication about this virus has been abysmal, and this is just another example.
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I mean, Iām sure they justified it to themselves some other way. Iām being cynical here. But the WHO was under a lot of pressure to avoid admitting it was aerosol.
A lot of ānoble liesā being told, imo.
Iām interested if covid can also spread through droplets. I have never heard that it doesnāt.
Yes, it can. I mean, how could it not?
Of course it can & does spread by droplets - thatās just not the primary mode of transmission.
I think at this point most serious people have dismissed surfaces as anything but a very rare mode, if even that.
There was some research out of Australia a while back that posited it could also spread through flatulence. You might think Iām joking but a lot of people have suggested there may be a fecal-oral transmission route (which is how norovirus primarily spreads), mostly due to viral shedding in feces for weeks from infection.
Even from the earliest outbreaks (eg Diamond Princess cruise, WA church choir), there was more evidence for aerosols or fecal-oral than strictly droplets.
Maybe droplets arenāt āprimaryā. I havenāt seen that. So 1-49% for droplets? And masks prevent some low % of aerosols?
Stop pretending itās zero. Masks might actually be be useful in public settings where low duration exposure is most likely, and droplets are probably a meaningful transmission risk without them.
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Iām not pretending. Cloth & surgical masks may block some droplets & filter some percentage of aerosol particles, but thatās not blocking transmission.
Do you have any idea how many aerosol particles are emitted with each and every breath of a symptomatic infected person, and how many of those take a path of least resistance around a mask, rather than trying to get through (plenty get through cloth & surgical masks anyway)? Now multiply that by the number of breaths someone exhales in a minute, an hour, or a full day at school, & compare that to how few virions it takes to infect someone.
The effect on transmission is effectively zero.
Forgive me for using āmasks donāt workā as shorthand for this more nuanced explanation for why masks are effectively doing zero to affect covid transmission rates.
Thatās not even getting into the tendency of masks to aerosolize the droplets that do get caught in them through plosive force, breaking them up into those tiny particles that hang in the air for hours; or their ability to nebulize droplet particles on inhalation, making smaller particles that go deeper into the lungs.
Just on the covid front alone theyāre not really doing much if any good & possibly a net negative. Thatās before even considering the ancillary health & psychosocial harms, not to mention unintended economic & environmental effects: how much is being spent by individuals & governments on masks that provide effectively no benefit, and what are the opportunity costs (better ventilation, better nutrition, paid sick leave, etc); how much waste is being created by all the disposable masks - at this point it makes the concern about plastic straws look downright laughable; masks are warm moist petri dishes strapped to faces, they cause acne & other skin infections in some who wear them for long periods; they cause anxiety/panic attacks in some people, especially some abuse survivors & others with PTSD; they inhibit communication, especially for the deaf or hard of hearing who rely on seeing lips, not to mention cutting off a significant part of nonverbal cues; as promoted (incorrectly) as both protection and source control they encourage people to engage in long-term cognitive dissonance of treating themselves & others as simultaneously both infectious & vulnerable; they dehumanize us, and are a constant visual reminder to be afraid & view our fellow humans as vectors of disease.
So, no, Iām not pretending itās zero. Masks - and particularly mask mandates, especially on children as young as 2 years old - are a clear net negative. That so many people donāt see that makes me weep for humanity.
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Sheesh just stop with this nonsense. Itās a minor inconvenience at worst.
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why donāt you do the calculation for us, with references for the numbers you use ? Your writing here seems to imply you know what they are. For example, how many moles of air molecules go around to mask? What is the density of virus per mole, and how does this depend on the health of the person? How does the probability distribution of infection vary with the number of virus particles?
In all seriousness, I donāt think most of these quantities are well understood. I donāt think the spread of covid is particularly well understood.
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I literally posted an article that did that. It has a lot of math, so it wasnāt the easiest article to read. But it concluded (pre delta) that masks reduce transmission substantially in a typical school setting. Even fabric masks. As i mentioned above, that result may not hold up with Delta, and Iād recommend switching to something like a kf94, or at least a surgical mask.
And MARCIE posted an article that linked to some group that was collecting data from a huge number of schools, and, surprise!, it found that teachers were less likely to get infected in schools with mask mandates, if you held the other factors constant.
As for masks retaining moisture and creating a āPetrie dishā: there were a couple of good studies before covid that found that higher humidity reduces the likelihood of catching respiratory bugs. One was done in a school, where they added a humidifier to half the rooms, and the other in a hospital setting. Westerners live in an abnormally dry environment, and itās not good for the immune system in the respiratory tract. Dry air is probably a major cause of āseasonalā respiratory bugs. When there was only epidemiological data that masks help, and not theoretical data, many researchers believed that increasing the moisture content of the air you breathed was 100% of the benefit of masks.
They are cheap, and no one is failing to open windows or to provide sick leave because masks cost too much.
That masks remind us that thereās a pandemic out there is part of their value. It turns out that people who wear masks touch their eyes less, not more. (And touch their nose less, of course).
Masks do reduce the volume of your voice. And some (not all) masks also distort the sound of your voice. They really are problematic for those with partial hearing loss, as well as the deaf who read lips. And if there are any infants whose primary caregivers are always masked, thatās probably not good for their development.
And they are problematic for certain people who are autistic, have PTSD related to breathing/choking, and a few other psychological disorders. And many people find them uncomfortable. I recommend shopping for masks you find moderately comfortable. A cheap, reusable strap around the back of your head, to take pressure off the ears, helps many. A good fit also reduces issues with glasses fogging up. Iām surprised Marcie didnāt mention that, as thatās probably the most common actual problem.
There are disposal issues, as with any other consumable item. Iād guess they are not as big a problem as plastic grocery bags, but Iām sure they are a bigger problem than plastic straws. But i donāt believe there was ever a significant issue with plastic straws. If you use disposable masks, dispose of them properly, and donāt drop them in parking lots, or leave them perched at the top of unprotected outdoor trash cans.
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Oh hey, how timely. Hereās a WSJ article that cites two studies that found that a school mask mandate reduced (study 1) transmission traced to those schools and (study 2) rates of pediatric covid in the corresponding counties
that link is supposed to be free for non-subscribers to read.
links and summaries of underlying studies
Iāve bolded the outcomes.
Schools in Maricopa and Pima Counties, which account for >75% of Arizonaās population ( 2 ), resumed in-person learning for the 2021ā22 academic year during late July through early August 2021.
ā¦
The association between school mask policies and school-associated COVID-19 outbreaks in Kā12 public noncharter schools open for in-person learning in Maricopa and Pima Counties during July 15āAugust 31, 2021, was evaluated.
..
A school-associated outbreak was defined as the occurrence of two or more laboratory-confirmed COVID-19 casesĀ§ among students or staff members at the school within a 14-day period and at least 7 calendar days after school started, and that was otherwise consistent with the Council for State and Territorial Epidemiologists 2020 outbreak definitionĀ¶ and Arizonaās school-associated outbreak definition.**
schools with outbreaks that started less than 7 days after they opened were excluded. They ended up using 96% of the data they started with after exclusions like that.
They found that masks reduced outbreaks by a factor of 3.5 or so.
In the crude analysis, the odds of a school-associated COVID-19 outbreak in schools with no mask requirement were 3.7 times higher than those in schools with an early mask requirement (odds ratio [OR] = 3.7; 95% CI = 2.2ā6.5). After adjusting for potential described confounders, the odds of a school-associated COVID-19 outbreak in schools without a mask requirement were 3.5 times higher than those in schools with an early mask requirement (OR = 3.5; 95% CI = 1.8ā6.9).
the researchers used data from counties:
- data from July 1āSeptember 4, 2021
- at least 3 weeks with 7 full days of case data since the start of the 2021ā22 school year
- the county had known and consistent mask rules
Among the 3,142 U.S. counties included in the initial sample, 16.5% (520) were included in the final analysis after applying the selection criteria.
They normed by time since school opening, and for a host of demographic stuff, and focused on change in rate across the weeks from before opening to after opening.
Comparisons between pediatric COVID-19 case rates during the weeks before (weeks ā3, ā2, and ā1) and after (weeks 0, 1, and 2) the start of school indicate that counties without school mask requirements experienced larger increases than those with school mask requirements (p<0.05). After controlling for covariates, school mask requirements remained associated with lower daily case rates of pediatric COVID-19 (Ī² = ā1.31; 95% confidence interval = ā1.51 to ā1.11) (p<0.> 001)
The findings in this report are subject to at least four limitations. First, this was an ecologic study, and causation cannot be inferred. Second, pediatric COVID-19 case counts and rates included all cases in children and adolescents aged <18 years; later analyses will focus on cases in school-age children and adolescents. Third, county-level teacher vaccination rate and school testing data were not controlled for in the analyses; later analyses will control for these covariates. Finally, because of the small sample size of counties selected for the analysis, the findings might not be generalizable.
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Oops, I missed that article. I have seen some articles that model some of the aerodynamic involved with covid spread, but donāt remember ever seeing a fermi-back-of-the-envelope style calculation that the other post seemed to be referring to.
I think i agree with everything in your post. I wasnāt trying to say masks donāt reduce transmission, or that we we shouldnāt be wearing them.
But i believe there is still a a lot mysterious about how covid spreads. Admittedly i donāt follow the mask articles all that closely, because i am already convinced we should wear them. However, i remember reading that there is a lot of variance between how much people spread it. In other words: why are super spreader events apparently so important to the spread of covid, and why do they happen? This is not so much uncertainty in what policy should be, but in the detailed science. And why donāt children get as sick, and how does this affect how likely they are to get it? Or why does so much spread seem to happen within family groups as compared to between them? Have masks really stopped in-school transmission or not (which is hard to measure since there is so much out of school contact too)? And so on. Some of that could easily reflect my own ignorance, but i think there are still some very important open questions.
Most of my post was meant to respond to Marcie, not you. I agree that thereās still a great deal we donāt know. The number one mystery is how a disease can both be so mild in nearly half the people it infects that they literally donāt notice it (45% are asymptomatic) and yet have a rather high kill rate. Thatās unusual.
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This is a totally random thought with no extremely little science to back it up.
I wonder if the variance of the health of people is greater in 2021 than in the past.
More people who are morbidly obese and have or are developing cancer on the one hand. But also people who exercise and eat healthy diets and have access to quality health care.
So due to greater variance in health compared with, say, 1918, we have a greater variance of outcomes.
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What about cross immunity from other coronaviruses?
Also, t-cell immunity response in half of blood samples from before COVID
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