The experiment that proved airborne disease transmission
jhsph.edu
jhsph.edu
What X is large enough to ensure that all the virus particles you cough out end up at the collector? Is it possible to do this without electrocuting everyone?
Humans are a bit more complicated in structure than say a metal ball, but my guess would be that there would be a similar situation where all the free electrons would just build up on the skin. Therefore, I don't think the particles one would cough up would be negatively charged.
No idea how that influences where the electrons go.
I wonder how the nervous system would interact with that as synapses fire. I'm curious if they would build up, or if the synapses all over the body firing would make them bounce around constantly.
> No idea how that influences where the electrons go.
Electrons don't specifically move toward surfaces, they move to be as far apart from each other, so internal surfaces don't count significantly. Saying they move toward surfaces is only true for convex objects (and they are evenly distributed when the object is a sphere).
In the human body, they'll move toward extremities: hands, feet, tips of hairs, ...
The latter is an easy to observe effect of static electricity, charges will apply pressure on the hairs and make them straight so they are as far away from the rest of the charges as possible. See the first image here for example: https://www.loc.gov/everyday-mysteries/item/how-does-static-...
So if you take the naive approach -- which is wrong, because charges live on surfaces, not in volumes -- you would want the person to have about a coulumb of charge to ensure that 1 extra electron was allocated to each virus particle.
Whether or not 1 electron per virus is enough is a separate question, but that gives you a lower bound -- if you are allocating, say, 0.1 electrons, only 10% of your virus particles will have a charge.
Edit: so, given the capacitance of humans as 200 pF, that would be 5 gigavolts?
I'm curious as to why this logic doesn't apply to the electrostatic precipitator. Or maybe it does and we just have too much capacitance?
https://en.m.wikipedia.org/wiki/Electrostatic_precipitator
ETA: the EP causes Corona discharge, which doesn't sound like it would be too pleasant if you were the electrode.
"The Multiple Wave Oscillator is a combination of a high voltage Tesla coil and a split-ring resonator that generates ultra wideband electromagnetic frequencies."
The ionization of the air in the main room was quite intense, with plasma freely forming coronas.
Once the pandemic is over, you can drive out to get a 'sound bath' in the room, if you are so inclined.
[0] Assuming the capacitor didn't fail -- in the case of actual capacitors, they only operate within certain parameters and tend to explode outside of them, in the case of people in an atmosphere, you'd probably see those discharges well before you managed to shove a full coulomb of charge onto one.
https://timesofindia.indiatimes.com/city/delhi/why-viral-loa...
Places like hospitals filter the air internally to reduce infection.
Is this something a household HVAC could be upgraded to. Do HNers in areas that have air con think it's a "yeah people will want that" idea?
If the required power is,say, 500w continues, or more, that's going to get quite expensive to run.
For example, where I live running a 500w device 24/7 is going to add an extra $1100 a year to the power bill.
Looking at random in-duct systems, it looks like they range from 1 to 10 or so bulbs with the later being for commercial buildings. Home systems seem to lean toward 1 or 2 bulbs of maybe 20ish watts or so total. This site [2] says typically $15-30 per year energy cost
[1] https://www.1000bulbs.com/product/113917/AU-LG64T5L.html
Interesting bit on how UV-C works to sterilize.
https://en.wikipedia.org/wiki/Pyrimidine_dimer
Interesting thing bacteria and some viruses have DNA repair enzymes that can fix damage from UV-C. Medically you're always bedeviled by bacterial and fungal spoors.
Limitations with UV-C sterilization I think prevents wider use. Not a magic bullet. Though it probably works well for influenza, colds, and this bat virus.
Again, what is safe .. but it the infrastructure is there ...
Just vent it out in the open air and not on people.
Terrible for energy efficiency
Et voilà, now it's no longer terrible for efficiency since you're recovering 70-90% of the energy. For fixed-plate exchangers there's no cross-contamination, either.
There's evidence that people that have been exposed to previous, weaker, coronaviruses are more likely to have mild responses to Covid-19, for example.
[1] http://www.uvresources.com/blog/the-ultraviolet-germicidal-i...
For a residential recirculating system, the relevant parameter is flow rate times fraction of particles removed in one pass. An AC or heater generally has a high flow rate and needs a filter to keep the heat exchanger and fan clean regardless. The added material and energy cost of a good filter is low.
On the other hand, if you are moving air from one space to another and don’t want to contaminate the space you’re moving air to, the absolute filter / sterilizer efficiency may matter. Things like HEPA may be useful here.
I would be surprised if a UV lamp is cost effective for new installation. For retrofit in a system that can’t handle a better filter, maybe.
https://www.climask.com.tr is interesting. Like a face mask on AC unit. Nano-silver is effective against bacterias and viruses. And having a filter with nano-silver coated surface is just a simple yet an effective approach. Cost-wise changing a good quality air filter every 2-3 months is much cheaper than having a UVGI installed and paying higher electricity bill every month.
> they constructed an air-tight closed ventilation system that connected a six-room tuberculosis ward to an exposure chamber with 150 guinea pigs. (Among rodent animal models, only guinea pigs could cough and sneeze, making them ideal for studying how respiratory diseases spread.) The guinea pigs were exposed to the infected air over a four-year period. A second group of 150 guinea pigs acted as controls: their air ducts were irradiated with UV-C lamps to kill TB bacilli.
Results:
> an average of three guinea pigs per month contracted TB, while no controls were infected. The experiment [also] quantified how many TB infections could be expected to result from exposure to a given number of patients over a defined interval.
Relevance to COVID-19:
> Riley’s research points to wearing masks and disinfecting air in enclosed spaces as two of the most effective tools for fighting COVID-19
> The animals were used so frequently as model organisms in the 19th and 20th centuries that the epithet guinea pig came into use to describe a human test subject.
Among my friends, to go first in an uncertain situation is sometimes called, "poodling it".
- It contains no experimental data, it's a review of possible methods.
- It's not about Covid-19, although that's to be expected.
- The masks it talks about are N95 and N100 respirators (which it notes aren't in adequate supply).
Some interesting quotes:
> If one assumes that influenza is transmitted by respiratory droplets [..] rather than by aerosols [..], the supposition may be that keeping a safe distance may obviate the need for a mask. It is stated that the range of such droplets is generally no more than 3 ft. We are unable to locate the basic science behind that assertion.
> Whether contagious as a respiratory droplet, aerosol, or both, there have been no controlled studies to investigate the efficacy of respirators in preventing the transmission of influenza A
> there is a theoretical problem in the logic underlying N–95 respirators. Assume an N–95 mask functions better than its rating and at a sedentary inhalation rate blocks 98% of the bioaerosols that it is confronted with. We are still left with the 2% that penetrate through the filter, to be inhaled by the wearer. Whether discussing tuberculosis, influenza, measles, or smallpox, we do not know the concentration of pathogenic bioaerosols in the environment, nor do we know the minimum infectious dose for these pathogens.
Anyway I don't think anyone disagrees with their conclusion that having everyone wear N100 masks is a good idea, but I'm not sure if any of their proposed methods are feasible. And the most important conclusion of their research is perhaps that we know way too little about possible countermeasures.
It requires you wear the mask at all times. And that you change it regularly by removing folding inwards and disposing securely.
Otherwise you may pick up an infection and then put a mask on afterwards which necessarily means that much of the shedding caught in the mask will be breathed back in - From mouth to nose and vice versa.
Or put the mask back on backwards or wave it around in the air, put it on surfaces and the like.
All of which amplify the current infection you have making you more infectious when you take the mask off.
And may explain why at a local Covid secure school they all went down with the usual back to school viral cold far more rapidly this year than they normally do.
What we don’t know - because we’re not hamsters permanently in cages - is what the network effects are.
https://www.healthaffairs.org/doi/pdf/10.1377/hlthaff.2020.0...
> Mandating face mask use in public is associated with a decline in the daily COVID-19 growth rate by 0.9, 1.1,1.4, 1.7, and 2.0 percentage points in 1–5, 6–10, 11–15, 16–20, and 21 or more days after state face mask orders were signed, respectively.
I'm trying to sort of if those percentages are absolute or relative. I think they're absolute because some of the graphs are labeled "percentage point change," but using absolute percentage point changes for an analysis like this is seriously flawed because a 2% reduction could range anywhere from a miracle to statistically significant, but negligible.
It's also not clear if people feel safer wearing face masks, so they engage in riskier activities.
My guess is they're not as effective as claimed because while the Bay Area has pretty high compliance, if masks were systemically very effective, we'd see case rates drop a lot faster, not still be above mid-June numbers. That said, whatever the Bay Area is doing right now is working.
Wearing masks is an entirely different thing, and would need an entirely different test.
Even the original experiment leaves questions for me. How does one diagnose TB in guinea pigs? What health state were the guinea pigs in? Was there a familial predisposition to respiratory illnesses for some of these? What conditions were they kept in? Etc.
Not an expert on radio isotopes or spectrography or viruses.
Note: I know, radioactive virus at this point might freakout people a little.
https://nextstrain.org/ncov/global
Our ability to do this for every single Covid-19 case in the universe is, I imagine, limited only by funding/infrastructure/training.
See for example https://www.eurekalert.org/pub_releases/2020-10/du-gt100120....
Also you wouldn't mutate a virus with C14 or similar radiactive isotope, because that can't be encoded in its genetics, and such a virus would use any old Carbon atom (most likely normal C12) to replicate.
Finally, mutating a virus and releasing it seems ethically dubious in the middle of a pandemic...
Also the fact that mandatory masks have had zero effect on the R value in any country, same as for influenza and other "flu" viruses. If it was spread by droplets/surfaces then masks should at least have some effect to slow or contain the spread, like make a dent in the curves.
Yes there are masks that prevent TB transmission but this bacteria is more than 10x larger than typical respiratory viruses. They look like duck beaks, are very uncomfortable and require training to use properly. I haven't seen these anywhere during this pandemic and they wouldn't help either as they are designed to prevent aerosols down to about 2um size. There is plenty of space for ~0.1um viruses even in 0.5um droplets. Some researchers even claim the virus can stay potent a while after the droplet evaporates and float around like dust.
CDC meta study showing medical masks had no effect neither as PPE or source control: https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article Study comparing medical masks and N95 masks found no difference in transmission of influenza: https://pubmed.ncbi.nlm.nih.gov/31479137/ More links and summaries collected here: https://swprs.org/face-masks-evidence/ This Time article has lots of links and info (but the argument for masks is complete fail): https://time.com/5883081/covid-19-transmitted-aerosols/
It's funny how some claim we didn't need masks before, but now we need them since it's spread by aerosols?? The truth is in fact the opposite and don't get me started on cloth masks...it's absurd. This seems more like covering their asses than following the science.
Most of these studies involve health personell, with high-end masks, the general public will of course do much much worse. This survey of studies and history of mask use in dentistry is also informative (why was it taken down?): https://archive.is/My2jr
The WHO reversal on mask use is also revealing: On July 12, Deborah Cohen, the medical correspondent of BBC2’s Newsnight, revealed on Twitter that: ‘We had been told by various sources [that the] WHO committee reviewing the evidence had not backed masks but they recommended them due to political lobbying.’ She said the BBC had then put this to the WHO, which did not deny it. In March, the WHO had said: ‘There is currently no evidence that wearing a mask (whether medical or other types) by healthy persons in the wider community setting, including universal community masking, can protect them from infection with respiratory viruses, including Covid-19.’
-Van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, et al. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N Engl J Med. 2020;382:1564-7. -Fears AC, Klimstra WB, Duprex P, Weaver SC, Plante JA, Aguilar PV, et al. Persistence of Severe Acute Respiratory Syndrome Coronavirus 2 in Aerosol Suspensions. Emerg Infect Dis 2020;26(9). -Chia PY, for the Singapore Novel Coronavirus Outbreak Research T, Coleman KK, Tan YK, Ong SWX, Gum M, et al. Detection of air and surface contamination by SARS-CoV-2 in hospital rooms of infected patients. Nat Comm. 2020;11(1). -Guo Z-D, Wang Z-Y, Zhang S-F, Li X, Li L, Li C, et al. Aerosol and Surface Distribution of Severe Acute Respiratory Syndrome Coronavirus 2 in Hospital Wards, Wuhan, China, 2020. Emerg Infect Dis. 2020;26(7). -Santarpia JL, Rivera DN, Herrera V, Morwitzer MJ, Creager H, Santarpia GW, et al. Transmission potential of SARS-CoV-2 in viral shedding observed at the University of Nebraska Medical Center (pre-print). MedRxiv. 2020 doi: 10.1101/2020.03.23.20039446. -Zhou J, Otter J, Price JR, Cimpeanu C, Garcia DM, Kinross J, et al. Investigating SARS-CoV-2 surface and air contamination in an acute healthcare setting during the peak of the COVID-19 pandemic in London (pre-print). MedRxiv. 2020 doi: 10.1101/2020.05.24.20110346. -Liu Y, Ning Z, Chen Y, Guo M, Liu Y, Gali NK, et al. Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals. Nature. 2020;582:557-60. -Ma J, Qi X, Chen H, Li X, Zhan Z, Wang H, et al. Exhaled breath is a significant source of SARS-CoV-2 emission (pre-print). MedRxiv. 2020 doi: 10.1101/2020.05.31.20115154. -https://pubmed.ncbi.nlm.nih.gov/19797474/ -https://pubmed.ncbi.nlm.nih.gov/19216002/
"Most studies were underpowered because of limited sample size, and some studies also reported suboptimal adherence in the face mask group"
https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article
And indeed you can sympathise with them that it would be hard to perform such an experiment.
But the whole point of science is that it allows us to make predictions based on theories. And the current scientific consensus is that wearing masks is beneficial.
I don’t know why there hasn’t been more discussions about the consequences of this though.
For example, with airborne transmission, 6 ft distance is not enough, you need > 30 ft, e.g. if you are inside with poor airflow for a long time with someone who is infected, good luck (unless you have a good N95).
Russian FSB has just arrested (on secret state security charges) on his short trip back home from China a top high voltage systems specialist who has been working for the last two decades on UV water and air cleaning system in South Korea and China. Seems it is becoming a sought after hot tech in the current situation.
Unfortunately, air purifiers have embraced the situation by demanding luxury pricing.
So you can smell ozone well before it is in the harmful range. Some air circulation wouldn't hurt while the device operates, but napkin math says you are OK.
Edit: some sizes here, including SARS-CoV-2
https://www.news-medical.net/health/The-Size-of-SARS-CoV-2-C...
Then there are super-resolution techniques which can go beyond that, but I don't think any of them could be adapted to scan the vicinity of the coughing human in real time.
> The current guidance from numerous international and national bodies focuses on hand washing, maintaining social distancing, and droplet precautions. Most public health organizations, including the World Health Organization (WHO) [16], do not recognize airborne transmission except for aerosol-generating procedures performed in healthcare settings. Hand washing and social distancing are appropriate but, in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people. This problem is especially acute in indoor or enclosed environments, particularly those that are crowded and have inadequate ventilation [17] relative to the number of occupants and extended exposure periods (as graphically depicted in Figure 1). For example, airborne transmission appears to be the only plausible explanation for several superspreading events investigated that occurred under such conditions [10], and others where recommended precautions related to direct droplet transmissions were followed.
Indoor contact, proper veneration, etc causing super-spreader events.
Meanwhile here in Canada they waited until late May to even recommend wearing a mask in such situations (other countries like the US had similar time frames and Dr Fauci openly admitted they withheld this recommendation for the benefit of healthcare workers).
https://www.ctvnews.ca/politics/it-s-now-recommended-that-ca...
Much like drug prohibition and other grand social control experiments, I'm not convinced the value of being vague or simply straight up not recommending masks in order to keep supply chain available for healthcare workers was ultimately worth the downside.
If supply chains was the issue then spend the government law enforcement power controlling and directing the supply chain for medical quality masks. This 4 month experiment (and I'm being generous there) where Feb, Mar, Apr and most of May they spent creating confusion and not recommending masks ultimately did more harm than good.
Now pundits and online commenters love to attack these anti-mask people when for much of the year expert sources were far from making masks the recommended choice. Including gov-delivered misinformation about their utility in order to explain themselves.
If the pro-social control (ie, lying the public) group thinks it was really stopping the wealthy and connected from completely ignoring these guidelines, then they are lying to themselves. As always with these gov poppet-mastery policies the only losers were the lowest common denominator poor people. Plenty of which still don't funny trust masks.
I would have rather spent four+ months explaining the virtues of masks and explaining the supply problem honestly. Than playing catch up last minute.
The fact Asia who had adopted masks, and never spent any time lying or dodging their public on their utility, have done better than western countries is no surprise. Asian countries had masks well before COVID.
The older I get the more cynical I become about government and intelligentsia 'we know whats best', that includes withholding information (something extra popular in healthcare). All information should be as transparent as possible, regardless of fantasies of controlling it.
Who says that saying its airborne "has" to mean that certain procedures have to be adopted? That's not a rule of the universe, it's a rule that humans came up with and agreed upon and humans have the power to fix. We distilled down a set of physical principles into a set of guidelines, forgot the underlying physical principles and now operate purely in the world of the manmade guidelines, totally oblivious to when the guidelines are no longer reflecting the physical reality.
To be a bit more concrete, consider the following: if you have a system where people are not encouraged to follow the rules as written, they will work against the spirit of what is written as well as what is actually written. If you have a system where people are discouraged from not following the rules, they may still engage in things that do not follow the spirit or written rules, but there is some accountability. But you can also try to work around what’s written to follow the intent as well, and I think that is where you get weird, counterintuitive, “stupid” results that can still “make sense” (as opposed to clearly corrupt cases where it is “stupid” and also does not make sense.)
I think people, especially literal minded as many here are, prefer concrete rules. But the knock-on effect is that its not easy to simply proclaim they’re made up any time it’s inconvenient, and it really shouldn’t be. Perhaps, in fact in my opinion, definitely, the “escape hatches“ for when rules don’t work out practically are broken, but I still do prefer having rigid standards, especially for health.
Hopefully, although it is probably not going to happen, organizations can have some postmortem-style reflections on what went wrong, so that hopefully next time we can be better prepared. History loves repeating though, so, you know.
Or perhaps in a different light, neither do the people who would've died if we had chosen a different branching path with negative consequences. There is some implication that there was a better outcome easily available and that is not clear at all. There should've been one, but there wasn't necessarily.
Also how do you keep information from the public without keeping it from hospitals. Widespread publicising of a controversial tidbit to hospitals would leak within the minute if not within the hour ..
I'm not saying I agree with how it was handled at all .. I'm merely pointing out the fairly obvious realities to the claims made, which seem strong on principle but lacking in pragmatism and consideration of the realities.
https://www.nytimes.com/2020/09/30/world/europe/ski-party-pa...
Turns out the "don't close borders" advice was a cached thought related to a plague outbreak in India over 25 years ago, and welded in place by politics.
We would have had to prepare with 10 years of 24/6 manufacturing of N95s to stop an airborne virus, which is why the most effective response is social distancing (not going to work, the 6 ft thing is bunk).
Of course they are present in the smallest droplets! They are present in the mucous secretions of the infected individual and they will get expelled through the big and the small droplets.
The distinction shouldn't be a qualitative one, airborne vs not airborne. It's a quantitative one, sufficiently infectious viruses may pose a risk at much smaller doses, the kind that you may be exposed by the smallest droplets expelled that simply stay afloat.
It's also worth noting that human immune response is a complicated beast, what may not be infectious for an average healthy individual may put down someone with a weakened immune response. So even supposedly "not airborne" viruses that are very unlikely to infect the average healthy individual at very small doses may pose an "airborne" risk for individuals with a weakened immune response.
There are more factors in all of this, atmospheric conditions may play a role. For example, cold temperatures may be more suitable for the virus to remain infectious outside of a host, thus increasing the likelihood of "airborne" propagation.
TL;DR: The distinction between airborne and not airborne viruses is an artificial one. That only makes sense statistically for an average individual at certain atmospheric conditions for a concrete strain of the virus. But as any real-world statistical distribution there are tails and you will find "airborne" qualities for pretty much any respiratory virus in those tails.