Close contacts with any unmasked exposure to persons with COVID-19 had significantly higher odds of receiving a positive SARS-CoV-2 test result compared with those who had only masked exposure. In addition, close contacts who had multiple exposures, whether masked or unmasked, had higher odds of a positive test result than did those with only a single exposure. The percentage of positive test results among close contacts in this study (30.7%) was similar to that observed in previous studies (approximately 31%) (2,3). Consistent with findings from studies in nonuniversity settings (4,5), the findings from this study reinforce that universal masking and having fewer encounters in close contact with persons with COVID-19 helps prevent further transmission in in-person university settings.
[….]
Wearing masks and having fewer encounters with persons with COVID-19 reduced the odds of transmission in a university setting. In addition, there was no evidence of secondary transmission from either of the two students with only masked exposure who received positive SARS-CoV-2 test results, and who, because of the modified protocol in place, were allowed to forego quarantine. Universities opening for in-person instruction could consider taking mask use into account when determining which unvaccinated close contacts require quarantine if enforced testing protocols are in place. CDC recommends that universal masking be adopted in indoor spaces for vaccinated and unvaccinated persons in areas with substantial or high transmission rates and that masks should be worn in indoor spaces in areas without substantial or high transmission rates if you are not fully vaccinated (9). In addition, CDC recommends COVID-19 vaccination for individuals aged ≥12 years.
Background
SARS-CoV-2 infection is transmitted predominately by respiratory droplets generated when people cough, sneeze, sing, talk, or breathe. CDC recommends community use of masks, specifically non-valved multi-layer cloth masks, to prevent transmission of SARS-CoV-2. Masks are primarily intended to reduce the emission of virus-laden droplets (“source control”), which is especially relevant for asymptomatic or presymptomatic infected wearers who feel well and may be unaware of their infectiousness to others, and who are estimated to account for more than 50% of transmissions.1,2 Masks also help reduce inhalation of these droplets by the wearer (“filtration for personal protection”). The community benefit of masking for SARS-CoV-2 control is due to the combination of these effects; individual prevention benefit increases with increasing numbers of people using masks consistently and correctly.
Source Control to Block Exhaled Virus
Multi-layer cloth masks block release of exhaled respiratory particles into the environment,3-6 along with the microorganisms these particles carry.7,8 Cloth masks not only effectively block most large droplets (i.e., 20-30 microns and larger)9 but they can also block the exhalation of fine droplets and particles (also often referred to as aerosols) smaller than 10 microns ;3,5 which increase in number with the volume of speech10-12 and specific types of phonation.13 Multi-layer cloth masks can both block up to 50-70% of these fine droplets and particles3,14 and limit the forward spread of those that are not captured.5,6,15,16 Upwards of 80% blockage has been achieved in human experiments that have measured blocking of all respiratory droplets,4 with cloth masks in some studies performing on par with surgical masks as barriers for source control.3,9,14
Filtration for Personal Protection
Studies demonstrate that cloth mask materials can also reduce wearers’ exposure to infectious droplets through filtration, including filtration of fine droplets and particles less than 10 microns. The relative filtration effectiveness of various masks has varied widely across studies, in large part due to variation in experimental design and particle sizes analyzed. Multiple layers of cloth with higher thread counts have demonstrated superior performance compared to single layers of cloth with lower thread counts, in some cases filtering nearly 50% of fine particles less than 1 micron .14,17-29 Some materials (e.g., polypropylene) may enhance filtering effectiveness by generating triboelectric charge (a form of static electricity) that enhances capture of charged particles18,30 while others (e.g., silk) may help repel moist droplets31 and reduce fabric wetting and thus maintain breathability and comfort.
Human Studies of Masking and SARS-CoV-2 Transmission
Data regarding the “real-world” effectiveness of community masking are limited to observational and epidemiological studies.
An investigation of a high-exposure event, in which 2 symptomatically ill hair stylists interacted for an average of 15 minutes with each of 139 clients during an 8-day period, found that none of the 67 clients who subsequently consented to an interview and testing developed infection. The stylists and all clients universally wore masks in the salon as required by local ordinance and company policy at the time.32
In a study of 124 Beijing households with > 1 laboratory-confirmed case of SARS-CoV-2 infection, mask use by the index patient and family contacts before the index patient developed symptoms reduced secondary transmission within the households by 79%.33
A retrospective case-control study from Thailand documented that, among more than 1,000 persons interviewed as part of contact tracing investigations, those who reported having always worn a mask during high-risk exposures experienced a greater than 70% reduced risk of acquiring infection compared with persons who did not wear masks under these circumstances.34
A study of an outbreak aboard the USS Theodore Roosevelt, an environment notable for congregate living quarters and close working environments, found that use of face coverings on-board was associated with a 70% reduced risk.35
Investigations involving infected passengers aboard flights longer than 10 hours strongly suggest that masking prevented in-flight transmissions, as demonstrated by the absence of infection developing in other passengers and crew in the 14 days following exposure.36,37
Seven studies have confirmed the benefit of universal masking in community level analyses: in a unified hospital system,38 a German city,39 a U.S. state,40 a panel of 15 U.S. states and Washington, D.C.,41,42 as well as both Canada43 and the U.S.44 nationally. Each analysis demonstrated that, following directives from organizational and political leadership for universal masking, new infections fell significantly. Two of these studies42,44 and an additional analysis of data from 200 countries that included the U.S.45 also demonstrated reductions in mortality. An economic analysis using U.S. data found that, given these effects, increasing universal masking by 15% could prevent the need for lockdowns and reduce associated losses of up to $1 trillion or about 5% of gross domestic product.42
Conclusions
Experimental and epidemiological data support community masking to reduce the spread of SARS-CoV-2. The prevention benefit of masking is derived from the combination of source control and personal protection for the mask wearer. The relationship between source control and personal protection is likely complementary and possibly synergistic14, so that individual benefit increases with increasing community mask use. Further research is needed to expand the evidence base for the protective effect of cloth masks and in particular to identify the combinations of materials that maximize both their blocking and filtering effectiveness, as well as fit, comfort, durability, and consumer appeal. Adopting universal masking policies can help avert future lockdowns, especially if combined with other non-pharmaceutical interventions such as social distancing, hand hygiene, and adequate ventilation.
[….]
[References follow.]
And, this from a member of the republican majority in the Missouri House:
Rep. Justin Hill @HillForMissouri
Replying to @Kip_Kendrick
Masks don’t work against COVID. 9:52 PM · Nov 14, 2020
Some of the responses:
@HillForMissouri what medical school did you graduate from?
@HillForMissouri another thing. From an ER nurse at Progress West today, where my mom in law tested + today. 6 dead on her shift last 24 hrs. 2 couples came in husbands passed. It’s going to be a bad winter. Stay in & wear a mask when out. Funeral homes cant keep up. Ur a liar
Can you walk outside in the cold & see your breath? Do you know why? Because it shows the aerosol droplets when you exhale.. this is an amazing visual of how the virus can spread.. guess what happens when you put a mask on?? It’s the craziest.. thing you don’t see your breath
I wonder how someone can be this dense, but then I see you attended Liberty “University.” The stranglehold conservatives have on Missouri will doom us all.
Look, sir. Your constituents are DYING because of this stubbornness. Masks are not a 100% miracle armor but YES there is a ton of evidence that they help prevent transmission. A LOT. It’s a cheap, painless way to HELP. Seat belts don’t work either if you don’t buckle up.
You think Rep Hill cares if people die? Come on…the man is staunchly pro-life because it’s ok to regulate a woman’s body but it’s a crime to force her to wear a mask to keep from killing actual people.
Really? Then why did MO Governor @GovParsonMO approve this new set of guidelines for MO schools which emphasize mask wearing? You could go spend a day in an ICU full of COVID patients, where you don’t wear a mask or need one, to prove your claim. Prove all of them wrong.
The ignorance Justin Hill is demonstrating with this tweet is dangerous and an embarrassment for his constituents. He is not fit for office.
You can scroll his Twitter for 2 seconds and find that out. Koolaid drinker if I’ve ever seen one.
What a jackass statement.
This is why your district has been called out by the physicians on the task force in recent weeks for increases in both case numbers and hospitalizations.
I could share scientific journals, including from the US Navy, to prove you wrong, but you wouldn’t care. Quite a dangerous game you’re playing with our lives.
Here’s a simple explanation
a mask reduces the distance a bunch of your spew goes
I make contact with less or none of your spew & I don’t end up getting your crud
Also, a mask helps limit the amount of crud I suck in
All documented by scientists which you are not one.
Based on this tweet alone, I can say you are no public servant.
The next time you go seek medical care please ask your doctor not to wear a mask and hope it’s not one of the many that still have to work while they are covid positive.
And this is exactly the reason why we’re not able to get the virus under control here.
He’s doing this for attention. Most of his tweets are “look at me, I’m so shocking”. We need leaders in this state, instead we have preformitive attention seekers.
Kinda like a life vest doesn’t keep a boat afloat or a parachute doesn’t prevent airplanes from falling out of the sky?
What doesn’t work against COVID is the GOP.
Yep.
You keep going out without one. The virus will beg to differ.
Actually, masks do help. Prideful ignorance, on the other hand, does indeed not work against COVID.
Science is impenetrable to the feeble-minded
That’s a lie that will get people killed.
Good to see you grew up, but you didn’t get over chugging lead paint.
That’s a lie that can cause death and the overwhelm of our health system. Who hurt you? Seek therapy.
This is ignorant and puts your constituents at risk. Masks work, so quit politicizing the issue.
Stupidity doesn’t work against the virus.
That Liberty education failed you…may want to ask for a refund.
Masks work. The doctors and scientists say they work. Crackpots don’t believe it.
And in your case, science doesn’t work against ignorance.
The ignorance just keeps on giving … just incredible
Bless your heart little man. Good to know you are so humble about your medical and scientific credentials #MOLeg
Got that good Liberty education, i see.
This is a reckless lie, Mr. Hill. Your constituents & all Missourians deserve better.
Repeating a lie does not make it true.
The Show-me State.
Because reading is hard.
Oh you dangerous idiot.
Dedicated public servant? That’s a joke.
Wait just a sec everybody, I’m sure an intellectual like Justin Hill just wants to have a good faith debate about the research he’s conducted which led him to contradict the prevailing consensus among public health/infectious disease experts. Lol jk, he’s weapons-grade stupid
You are not a scientist or medical professional. You are barely sentient.
There are no words for folks like you. To be raised by parents who hate and to pass that hate onto your children is truly remarkable. And that basically says everything about you. Satan will welcome you with open arms.
Stop with the Trumpist tropes. We all know about that article from last winter, and that there have been numerous studies of mask and covid19 that clearly demonstrate that masks most definitely work against this virus.
Keep up or go home.
You’re not very bright. That’s the tweet.
Masks do help to slow and prevent the spread of COVID
Asshole.
Masks don’t work against stupid.
Not only stupid but dangerous.
No wonder Missouri’s fucked.
Are you able to present empirical data to support that statement? If not, you are being reckless and irresponsible. Missouri deserves better.
Yes they do asshole
You don’t read much do you.
Fuckin clown show. Liberty education baby!
Found the liberty grad easily.
Goddamn do they feed you lead paint chips there or what?
You are proof nothing works against stupidity.
What? Are you stupid?!!!
Psychopath
Idiot.
Your stupidity is dangerous. That’s incredible really. To be so stupid that you’re a danger to the community. Pathetic
Justin…you’re easily be dumber than a bag of hammers. I swear the next time you park your stupid jeep in front of my house im going to get it towed. You are a sycophant and complete idiot endangering lives of your constituents.
There’s another story in there, don’t you think?
Damn you are dumb
You are as dumb as a rock. Is the earth flat in your world, too
My physician wife would strongly disagree with you. You absolute fucking MORON!! Come to the covid unit of the ICU without a mask. DM me for my number and I’ll hook you up. Seriously.
What are you, 12? Oppositional defiance? Grow up. Wear a damn mask.
You are an idiot. I could have sarcasm about it, but you are just an idiot, plain and simple.
You really must be some kind of stupid! Why don’t you volunteer in a COVID unit for 24 hrs and prove it!!
This arrived in yesterday’s mail (we let the mail sit, decontaminate it, and, in this case, microwaved it):
This, friends, is a misuse of public funds for partisan political campaign purposes. That asshole doesn’t even believe the stuff on the “b” side of the card, let alone understand the science and math of a pandemic.
When this is over, there better be a whole shitload of accountability and investigative hearings. No more fake “we need to look forward” comity for these sociopaths.
Large events and mass gatherings can contribute to the spread of COVID-19 in the United States via travelers who attend these events and introduce the virus to new communities. Examples of large events and mass gatherings include conferences, festivals, parades, concerts, sporting events, weddings, and other types of assemblies. These events can be planned not only by organizations and communities but also by individuals.
Therefore, CDC, in accordance with its guidance for large events and mass gatherings, recommends that for the next 8 weeks, organizers (whether groups or individuals) cancel or postpone in-person events that consist of 50 people or more throughout the United States.
Events of any size should only be continued if they can be carried out with adherence to guidelines for protecting vulnerable populations, hand hygiene, and social distancing. When feasible, organizers could modify events to be virtual.
This recommendation does not apply to the day to day operation of organizations such as schools, institutes of higher learning, or businesses. This recommendation is made in an attempt to reduce introduction of the virus into new communities and to slow the spread of infection in communities already affected by the virus. This recommendation is not intended to supersede the advice of local public health officials.
No gatherings of more than fifty for eight weeks. Eight weeks. This is not going away any time soon.
Jason Kander @JasonKander
The President trying to prevent the stock market from contracting coronavirus is the natural extension of believing corporations are people. 6:56 PM · Feb 24, 2020
The people haven’t been doing so well for the past two days.
Major averages slid on Tuesday, accelerating Monday’s sharp losses. The Dow fell 879 points, or 3.15%, the S&P 500 dropped 3.03% and the Nasdaq fell 2.77%. The U.S. 10-year treasury yield fell to its lowest level on record as the growing number of coronavirus cases outside of China continued to roil the markets, and investors[.]
Bad combover. Check. Too long red tie. Check. Orange spray tan. Check. Tiny hands. Check. Cluelessness. Check…
Senate Republicans are pursuing a federal health budget that omits funding for gun violence research, a proposal that Sen. Roy Blunt warns is too “controversial.”
[….]
Do you wonder why?
Which lawmakers got the most NRA money?
By Soo Rin Kim Feb 20, 2018, 8:51 PM ET
[….]
Sen. Roy Blunt: $4.5 million
Sen. Roy Blunt, R-Mo., has long been one of the biggest beneficiaries of NRA money. Not only has the group donated $56,500 to Blunt’s campaign committee over the years, the group has also spent $1.4 million bankrolling ads supporting him. The NRA also spent $2.5 million in 2016 opposing Democrat Jason Kander’s bid against the Missouri Republican.
[….]
