How many microbes does it take to make you sick?
quantamagazine.org
quantamagazine.org
Researchers will try to measure if some intervention like that works reporting binary PCR positive or negative- but we should want to know what was the severity of the illness. PCR positive with minor illness can be a good outcome indicating that the intervention helped lower the innoculum.
Some of those costs are hard to quantify scientifically or intangible e.g. restrictions on individual freedom, and even the scientifically quantifiable data may have large variability so you have to take an opionated position. Different cultures will obviously take different positions due to different weights they place on risks and values.
Therefore, at this point you leave the realm of science and enter the realm of politics. For whatever reason, people like to pretend it's entirely a scientific discussion but it's not.
I mean discussions are typically both science and politics. Masks lower the amount of people that get sick is scientific fact; why do you think they wear them in the operating room? Whether or not that is "worth" wearing a mask is politics though. However, if you want to convince people of something (aka politics) you may want to appeal to them using logic and for that you'll want to use facts.
Having large variability doesn't make something not a fact. Plenty of males 20-24 do not get in car accidents but that doesn't mean that none of them will or that if you were to insure say 100k males 20-24 and 100k females 20-24 that the males wouldn't in aggregate have higher claims. But given a specific male and specific female its entirely possible that the female gets into an accident first.
I used to think this way, but this advice needs to be conditional.
Dispassionate or distant parties can sometimes use facts to drive a decision. It's not even clear that it's the "correct" decision, since nobody has all the facts, and presentation, ordering, accessibility all matter tremendously.
Once you add an emotional reaction, well, people will logically or rationally pick or ignore facts to justify the emotion. Surely you've had someone tell you that you logically shouldn't be angry, and you greatly appreciated that insight and recalculated your emotions, right?
https://news.harvard.edu/gazette/story/2022/01/logic-or-emot...
The different words in "Pathos, Logos, and Ethos" all have their place and if somebody is acting emotionally it'd be better to use a Pathos arguement.
This article should be required reading, whatever your views on Covid and other conditions.
Although the attack method of the infection is significant, and the potential victim’s defenses are significant, the raw quantity of infectious agent and the exposure rate are also both important
Nothing is certain. Everything is statistics.
edit: Imagine this being controversial. I didn't realize there were Covid deniers and skeptics here, because what I've stated is completely within established science.
It would be nice to have some numbers to back this up. Let's suppose the "viral load" to acquire a Covid infection is 18 particles, the same as norovirus detailed in the article. And let's say you're exposed to hundreds of thousands of viral particles every minute you spend near a sick person [1]. If a mask reduces your viral load by 50%, is that a worthwhile method of avoiding infection?
Our simulation also shows that wearing a mask can effectively reduce the spread of the viruses.
Another metric is, will that stop you from getting sick? The threshhold is only 18 particles!
Given that, there will always be a border at which having an additional 50% coverage is useful. Where the actual line is, we don't know. But as long as protection is monotonic in the factors above, it's always valuable to have more protection, which implies even <100% effective masks are useful.
Trivial proof: Imagine someone with literally 10k masks all around them. You have to admit this is more safe than 1 mask. QED. You can call in meta factors like "in reality nothing matters" but you're arguing by consequences then, not actually disagreeing with the facts, just claiming they don't matter.
The issue with masks is one side started treating them like a talisman that makes infection impossible, which provoked the other side to say they do nothing.
On a population level, masks are probably close to ineffective against a viral pathogen. You can read the relevant Cochrane review to see that.
On an individual level they obviously do something, but you have to consider other factors as well, such as level/frequency of exposure and the like. Studies from prior to the pandemic suggested that a perfectly fitted N95 mask dramatically reduced flu virus penetration. For a more normally worn N95 the reduction was about 70%. For a surgical mask it was essentially nil. Importantly, a perfectly fitted mask required essentially gluing it to the face of a mannequin.
Final point is, with an intervention whose impact is measurable but imperfect, you have to consider the side effects. I personally know several friends of my teenage kids who now have odd (to me at least) social phobias for which the only “cure” is to wear masks everywhere. Just last weekend I was talking to a friend of my daughter who wears masks everywhere except indoors.
https://www.theguardian.com/commentisfree/2023/feb/27/dont-b...
The review concludes that we have evidence that masks are effective, but the set of papers reviewed cannot be used to conclude we know the level of effectiveness enough to make accurate judgements on tradeoffs in many of the kinds of situations where people were asked to wear masks in the pandemic. So we don't know enough yet.
I read a bunch of the criticisms of this paper and criticism of the anti-maskers misrepresentation of what it said, and none of the ones I found suggested that there were missed papers which provide the precision the review didn't find.
The Guardian article is a mixed bag in my opinion. It tries to get around the idea that we really need more research, it confuses a lot of things.
(BTW, I am not an anti masker, I wore a mask, I find people who whine about wearing them to be a bit pathetic most of the time.)
Is the surgeon wearing a mask to protect himself from me, or to protect me from him?
This article is factually accurate: https://www.wired.com/story/the-teeny-tiny-scientific-screwu...
Surgeons wear masks to protect the patient, because masks are very effective at trapping both droplets and aerosols that are emitted from the wearer. They are not designed to protect the user from lingering aerosols as masks are too loose to form a good seal, so most air breathed in simply enters from around the sides of the mask.
The idea that ballistic droplets are the primary means of infection is the old, old misunderstanding.
If we compare the objective of preventing transmission of pathogens from surgeon to patient to the objective of covering nudity, surgical masks are as effective as shorts.
Seeing as the objective is the objective, the ends should define the means. Therefore it is clear that any use of surgical masks is a fundamental and entrenched misunderstanding.
Surgical masks reduce outward aerosol-sized particles by at least 74%: https://www.nature.com/articles/s41598-020-72798-7
Surgical masks reduce outward COVID viral transmission by 73%, and viral RNA by 58%: https://journals.asm.org/doi/10.1128/msphere.00637-20
Outward filtering efficiency above 50% is certainly worth it compared to the cost of a surgeon wearing a mask. It's arguably worth it even at much lower efficiencies.
If you read my comment, you'll notice I'm not disagreeing on the aerosol/droplet size boundary. I'm arguing against the apparent subtext of your comment, which seems to indicate that surgical masks aren't effective at protecting patients.
I’d like to reiterate my analogy of the shorts :)
Not least due to the subtle knock-on effects: surgical masks cast a fog on public awareness of face-fitting masks, which are superior in all respects (including comfort, which – case in point – came as a surprise when I tried one).
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The effectiveness of face-fitting masks is so much greater that I honestly regard the use of surgical masks as morally indefensible.
From Cochrane.org:
Statement on 'Physical interventions to interrupt or reduce ... - Cochrane
Mar 10, 2023
Many commentators have claimed that a recently-updated Cochrane Review shows that 'masks don't work', which is an inaccurate and misleading interpretation. It would be accurate to say that the review examined whether interventions to promote mask wearing help to slow the spread of respiratory viruses, and that the results were inconclusive.
Repeating the important part:
the review examined whether interventions to promote mask wearing help to slow the spread of respiratory viruses
Conversely, here’s a good study that shows that consistent use of FFP3 respirator masks drastically reduced transmission among workers on a hospital ward: https://elifesciences.org/articles/71131
Note that the study only had the workers wearing FFP3 masks on shifts, and community transmission was high at the time. Therefore the study “leaked” and good masks work better than the numbers in the study might seem to indicate. Face-fitting masks do work, and very well. Of course they do. It’s all very clear if you dig into the aerosol physics.
A mask mandate that permits "wrap a piece of T-shirt over your mouth, some of the time, sometimes even covering your nose" (which is not far from what I saw for much of 2020) is, unsurprisingly, going to be more effective at ensuring grudging compliance with a mandate than it is to reduce the spread of an airborne virus.
Close family is at risk of severe illness or death from COVID. We provide for a small child. We do not have much margin.
I’d like to ask you to imagine the social repercussions of masking. It’s hard. I do not want to be weird. I do not want to be an outcast, practically speaking. I don’t want to wear a mask.
I just don’t have any margin in the other direction.
Also:
What is it about a hospital setting that makes a given type of mask more effective?
Answer: Nothing.
Hospitals are places where it’s easier to run a trial, and where it’s harder to avoid infection.
Face-fitting masks do not require glue. Fitting a mask isn’t that hard.
Cloth masks don’t work and never did.
The objective is to not die or be maimed by a virulent pathogen, or rather: to have the option. Clarity on effective means for those who want it. I want effective means because I need them. The objective is not social classification of mask wearers or categorization of discussion types or labeling people as cartoons.
The objective is clear information as input into serious personal decision-making. The guy on the subway is not in scope.
In terms of being weird: there are enough people wearing masks and most people literally care more about what they're going to have for dinner than whether or not you're wearing a mask. If a mask helps your family, don't worry about the epsilon weird aspect (as I'm sure you have already calculated).
I think I can also pretty decisively say that hospital purchasing optimizations give face-fitting masks a bad rap. The FFP2 masks that hospital staff wear here are cheap and very uncomfortable. This bleeds into society as a negative view.
There’s also another aspect: The difference between a N95/FFP2/whatever mask as part of the industrial production of a verifiable sanitization chain in a hospital on one hand, and on the other as a piece of fabric that’s ludicrously effective at stripping infectious particles from the air.
There are many more edge cases in a hospital, and many more pathogens. In private life – mine at least – it’s only really COVID that matters. In that case a mask can be reused again and again and it’s OK to touch it, basically.
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Re. being weird:
I don’t mind.
The weirdness hurts the family. There’s a big, big gap of dissonance between what we need to do and what public health authorities say. This includes flat out demonstrably wrong statements about transmission where I live. This dissonance makes the family weird, and it has caused severe social isolation of a mother with a young child.
I want to assure the reader that we don’t ask for much. We are very, very polite. We don’t demand anything, we are not difficult.
It’s purely the astounding dissonance. People don’t know what to do and just fade away.
It’s a very painful way to be weird. You feel it in your bones and your soul how unnatural it is.
I know my comment will just make you angry, because "you're different". But, maybe someone else will see it and consider their psychological state on this topic.
I wish for your life to be long and healthy; and the lives of your loved ones too. And in that, let me give you advice to trade for your judgement of my place in life and my actions and sacrifices and loss. The advice is this:
Read. The academic. Literature.
So what can you say? You see a stranger wearing a mask, you don't know if it's for a good reason or not. Probably the odds are that it's an emotional or psychological hangup, but it may be for a really good reason. So you need to just shrug and let people do what they think best for themselves. They're the ones responsible for themselves.
And the criticism of the Cochrane-method review.
And the studies not cited.
As well as the studies on the mechanics of transmission.
This somewhat excuses their reactionary stupidity. Like they weren't "provoked", the use of masks wasn't directed at them.
Here there was never an outdoor mask policy, so I didn't ever have a chance to evaluate my reaction to such a thing. There was apparently a policy banning stores like Walmart from selling seeds (which I interpreted as bureaucratic friction rather than intention, something that was born out relatively quickly in practice, and never in the minds of the reactionaries).
You can do some reading about the Bay Area and debates over whether government policies are in bad faith. I think it’s at least arguable that some are in fact in bad faith (meaning, no one really thinks they’ll serve any public purpose other than punishing groups of people).
The policy, not the global, some times lethal, pandemic.
The policy made people not want you near them.
My belief is that they were collectively responding to an uncertain, rapidly changing situation, were incentivized to be very conservative given the early experience in Italy, didn't adjust their approach sufficiently when new information revised the case fatality rate downward, and did a poor job overall of balancing the broad spectrum of risks and costs. I don't think any of these mistakes were intentional. And none of us, including those who criticize these policies in hindsight, really know what would have happened had the policies been more lax, especially early on.
There we are in perfect agreement.
That policy is also obviously at odds with scientific knowledge.
Policies like that harm high-risks groups immensely too.
Over here, the bad policies were strict social restrictions. Baseless and arbitrary restrictions of the number of people allowed to be at funerals and strict and severe limits to hospital visits. None of these were necessary from the perspective of the reality of aerosolized transmission and how easy it is to strip the pathogen out of the air we breathe.
It’s so absurd that it took a long time to find an analogy. It’s like repairing the flat tire on your bike with a patch of sod. It doesn’t really work, it’s messy, and people will think you’re crazy.
This is an oddly biased framing.
However there are statistics that areas with more masking had less severe illness. However that’s uncontrolled and some other factors or factors might account for both increased masking and reduced spread. That’s probably the case otherwise the RCTs would show efficacy.
All of the subsequent work is just computer models and doesn’t actually tell us anything empirical. Obviously it’s easier to create a model that produces the desired result than it is an RCT.
Science is an on going process, always open to being overturned.
To the point of masks - I agree with your statement here, but a regular mask (filtered masks should help to some extent) will not protect you from an infected person. An infected person with a mask will reduce the chance of spreading their viral load.
This detail is where I feel people are talking past eachother. Most of covid denial to me seems to be about a psychological reactance to being told to mask up when they are not sick.
One might argue that the extra chance of reduced vectorization is worth mask mandates, but that simplistic purely “scientific” approach is its own problem. You have to argue people where they are at and convince them, not force the “right” view on them and then get upset they are “in denial” or skeptical.
Or do you just mean universal requirements imposed by society at large when you say 'any'?
^ and the more you have it the less severe it is, until it asymptotically reaches a complete non-issue. As with the common cold.
I just don't get the rejection of basic facts.
Which is to say you shouldn't be terribly surprised that there is a general strain of "don't tread on me" in the discourse. Simply being told what to do is enough to elicit a strong negative response.
Infection is binary or not. You either get exposed to enough to actually result in replication inside your body or you don't. If you get exposed to a small amount and your immune system immediately eliminates it, that's not an infection.
The amount of exposure needed to actually cause an infection is different from person to person depending on their immediate immune response.
But it's not like reducing exposure by 50% reduces disease severity by 50%. Biology doesn't work that way.
What I wonder is if we can develop immunity (not boosting, assuming never been infected before) from being exposed to small doses, or do we need at least one full blown infection.
To test his theory, Dr. Jenner took material from a cowpox sore on milkmaid Sarah Nelmes’ hand and inoculated it into the arm of James Phipps, the 9-year-old son of Jenner’s gardener. Months later, Jenner exposed Phipps several times to variola virus, but Phipps never developed smallpox. More experiments followed, and, in 1801, Jenner published his treatise “On the Origin of the Vaccine Inoculation.” ... Vaccination became widely accepted and gradually replaced the practice of variolation. At some point in the 1800s, the virus used to make the smallpox vaccine changed from cowpox to vaccinia virus.
It'd be interesting to understand if that's true for all viruses and in what quantities.
For example, in the early days of COVID, we were told that being close to infected people outdoor did not expose us to enough viruses to get infected. Could such exposure have provided immunity?
The articles says exposure to tiny amount can "boost" immunity, which I assume means an immunity acquired earlier from a full blown infection (or vaccination).
Variolation for example, the predecessor to the world's first practice of vaccination (against smallpox) involved taking tiny amounts of live smallpox from scabs or pustules and giving them to people intentionally for a much lighter infection course that made them immune without the usually killing or horrifically disfiguring blow of a full smallpox infection. (look up photos of smallpox scars in survivors, warning, it gets graphic. Even many famous figures like Stalin were completely pockmarked by the scars of the virus for the rest of their lives, as you can see in unedited photos of the dictator)
It usually worked, but sometimes the patients got really sick anyhow and died. By the standards of the time, when fully a third of the population could expect to die from some epidemic disease or another, this was considered wonderful. Today it wouldn't be and thus the complexities of carefully calibrating vaccines.
I suppose one more dangerous thing with this, could be how popular anti vaccination ideas could become, when the anti-vaxxers start saying that vaccine is live virus
And that live pathogens are sometimes used should be known and discussed for the sake of clinical honesty and public health transparency. Either way, for any deeply dedicated anti-vaxxer, it probably wouldn't matter what they hear from even the best source. Once one's fixation on a concept becomes emotional or ideological, the subtleties and details of explaining contrary details stop mattering to them.
Taking random adjuvants consistently after minimal exposure to environmental antigens is more likely to give you deleterious allergies or issues associated with chronic inflammation.
so just describe the procedure, and call it a secret that big pharma doesnt want them to know, and theyre into it. be anybody but a doctor lol
slam dunk
My understanding of vaccine is that they use deactivated viruses but not small doses.
My question is about live viruses, and if we can get exposed to small doses enough that will trigger a immunization mechanism without triggering a full blown infection? Or does it work to boost an existing immunity only.
Some are weakened live agent. Some are killed or neutralized agent. Some are just a protein or other piece of the pathogen. Some like mRNA vaccines are code from the pathogen that causes your body to generate and then sensitize against something. There are probably other types.
I do find the oversimplification in the debate frustrating. Either all vaccines are bad or all vaccines are great when in reality each one is a different thing. As with other drugs some work better than others and some have side effects while others mostly do not.
As near as I can tell the mRNA COVID vaccine is fairly effective at reducing severity and duration of infection but not nearly so at completely preventing infection. There is a small risk of side effects but the danger from a more severe COVID infection is statistically much greater.
Creating a vaccine in a year is nuts. What we came up with is not half bad given that time frame. We will probably have much better COVID vaccines in a few years.
It's why there's been a lot of interest in inhalable vaccines[1] although getting them to market has had a lot of delays.
[1] https://www.nbcnews.com/health/health-news/nasal-covid-vacci...
I didn't write that you were, I wrote that I've gotten anti vaxxers to like vaccines with the same logic.
Its pretty clear that its coincidence that you didn't know your hypothesis was the basis of vaccination, regardless of your predilection.
You get a hefty dose of vaccine. The difference is that it's either not an infectious agent at all (just a fragment of one) or it's a low-infectious agent.
A phrase like "the raw quantity of infectious agent and the exposure rate" is calling attention to the fact that one brief intense exposure vs repeated small exposures over a long time span may have vastly different outcomes despite presenting your immune system with the same number of microbes to deal with.
I guess time is important here - the organism detects the initial virions and prepares defences - so if the infectious dose amount of virions comes after the organism is warned they fail to grow into an infection. But my intuition is that the complexity of that process and path dependence makes that infectious dose so variable - that it does not seem to be any useful.
An analogous process would be human fertilization: it technically only takes 1 sperm to fertilize an egg, but it's millions in order to make the probability of it happening meaningfully high enough.
Of course some viruses are stupidly good at this: it's estimated 5 norovirus particles will trigger a full blown infection.
When you are strong you are resistant. When you are weak you are susceptible. The difference can be huge.
It's a good argument for clean living, regular exercise etc.
What these articles don't talk about are the real-life challenges of concentration and contact time. For example, being a parent with a kid in school they might randomly sneeze or cough in my face while being completely asymptomatic. Then of course we all come down with covid later on.
Secondly, the claims about viral load and shedding have conflicting science on new variants too:
> https://www.nature.com/articles/s41591-022-01816-0#Sec7
i.e
> Nevertheless, in our study, correlation between RNA and infectious VL was equally low between fully vaccinated and unvaccinated Delta-infected patients, indicating that factors other than mucosal neutralizing antibodies may be important for the reduction in infectious VL
> Within 5 DPOS, we found higher RNA VLs but lower infectious VLs in swabs of unvaccinated patients with pre-VOC infections compared to Delta. These results disagree with other studies that analyzed only nucleic acid detection and found 3–10-fold-higher RNA copy number in Delta-infected patients compared to pre-VOC-infected patients
> Although VL is a key element of transmission, the process of human-to-human transmission is complex, and other factors, such as varying recommended protection measures, overall incidence, perceived risks and the context of contacts (household versus community transmission), can influence outcomes in the studies reported.
The best point from this article is the following:
> Transmission dynamics are complex, but the interventions we can take to protect ourselves are comparatively simple.
"Masking, increased ventilation and distancing reduces the number of microbes you’re exposed to. Vaccination increases the infectious dose. "
We really need to move beyond vaccine only, its not working Covid is just too transmissible.