Since Oct 9, 1999
Their conclusion: "Our findings indicate that a physical distance of 2 meters does not suffice to prevent transmission in environmental conditions such as those studied here; additional measures such as improved ventilation and airflow, installation of filtering devices or use of high-quality face masks are required to reduce the infection risk in these environments."
In other words, they are proposing using N95 masks, which would obviously need to be properly fitted, and with their valves they do not provide any source control.
22 July 2020 Adding Al Asmary: https://www.sciencedirect.com/science/article/pii/S120197120600124X: Unlike the above-mentioned report of ARI among Hajj pilgrims from Riyadh,6 in our study regular use of facemasks offered no significant protection against ARI. ...Furthermore, we found that intermittent use of surgical-type masks was actually associated with more than a 2.5-fold greater risk of infection. It is possible that once a facemask is worn in the presence of an infected patient, the mask could become contaminated with infectious material and touching the outside of the device could result in hand transmission of the infection to the respiratory tract during nose-rubbing.9 The study suggests (to me) that casual mask use similar to the "intermittent" mask use in the study is not useful and can actually be harmful.
A study of college dorms includes source control whidh is important to match the public mask use in the American experiment. The article https://academic.oup.com/jid/article/201/4/483/860983 talks about a study but does not give the specific numbers for effectiveness. They just say it is significant. They are referring to https://www.mm.dk/misc/maskermv.pdf and they show the results in Fig 1 which is worth looking at. The mask and mask/hand washers are not that much better off. I still believe that masks are better than nothing, but obviously based on these two studies people are going to have to decide for themselves.
21 July 2020 https://www.cidrap.umn.edu/news-perspective/2020/04/commentary-masks-all-covid-19-not-based-sound-data Short version: cloth masks don't really work. their effectiveness is not statistically different from zero. Nearly the same for surgical masks, although they are better than cloth. Most importantly the authors address the issue of source control. Many studies are based on ingestion control (someone who is not infected staying that way), not source control (someone who is infected not passing it on).
Their source control conclusion is that there is no or low effectiveness. My conclusion is that there is non-zero effectiveness based on ."There is moderate evidence that surgical masks worn by patients in healthcare settings can lower the emission of large particles generated during coughing and limited evidence that small particle emission may also be reduced." I would include speaking as part of my argument because speaking and coughing both release droplets.
17 July 2020 Just a quick update, the Jacobs study had only 32 people in it, and there was one cold in the maskless group and one cold in the masked group. That's the weakest study I have ever seen.
CDC study of the case of the salon I mentioned previously: https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm?s_cid=mm6928e2_w
16 July 2020 I still see the NEJM throwaway line cited: "We know that wearing a mask outside health care facilities offers little, if any, protection from infection" from "Universal Masking in Hospitals in the Covid-19 Era" The line is unsupported. The references aren't about masks. The paper actually supports wearing nasks in public by this line "More compelling is the possibility that wearing a mask may reduce the likelihood of transmission from asymptomatic and minimally symptomatic health care workers with Covid-19 to other providers and patients. " That's more true in public than in a hospital.
I also see this study now: "Use of surgical face masks to reduce the incidence of the common cold among health care workers in Japan: a randomized controlled trial" from https://pubmed.ncbi.nlm.nih.gov/19216002/ The study was not blinded and is only 33 people which is way too small. Also the specificity of the infection is debatable (not well defined)
10 July 2020 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7301882/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7301882/ I think that link was from Li'l Farmer. The paper basically says masks leak, but droplets are fairly large and many are stopped.
Another paper discussed in a thread: http://www.freerepublic.com/focus/news/3845416/posts:: Respiratory virus shedding in exhaled breath and efficacy of face masks
02 July 2020 Aguments for and against using masks to slow the spread of the coronavrius below. I wear one for work and wear it into stores even though a lot of people don't in rural Virginia.
We collected samples of exhaled particles (one with and one without a facemask) in two size fractions ("coarse">5 µm, "fine"≤5 µm) from 37 volunteers within 5 days of seasonal influenza onset, measured viral copy number using quantitative RT-PCR, and tested the fine-particle fraction for culturable virus. Fine particles contained 8.8 (95% CI 4.1 to 19) fold more viral copies than did coarse particles. Surgical masks reduced viral copy numbers in the fine fraction by 2.8 fold (95% CI 1.5 to 5.2) and in the coarse fraction by 25 fold (95% CI 3.5 to 180). Overall, masks produced a 3.4 fold (95% CI 1.8 to 6.3) reduction in viral aerosol shedding.
With speaking, the vast majority of droplets were above 0.5 microns https://www.nature.com/articles/s41598-019-38808-z).https://pubmed.ncbi.nlm.nih.gov/23505369/ It's not clear what the particle size distribution is and how that relates to the mesh. But cloth is probably inadequate: https://pubmed.ncbi.nlm.nih.gov/25903751/
With masks: the salon where two stylists tested positive: https://apnews.com/0abab24fa86efb702a259185e3074273 After about 14 days, there were no positive tests: https://www.facebook.com/SGCHD/posts/10158304982679378 46 tested out of 140, all negative, so a very low likelyhood (< 0.1% if the 46 are random) that any of the untested are positive.
Feb 13, 2016: "A system of government that makes the People subordinate to a committee of nine unelected lawyers does not deserve to be called a democracy." http://www.truthrevolt.org/news/scalias-full-dissent-same-sex-marriage-ruling
Sep 21, 2008. I'm putting this link: http://www.financialsense.com/fsu/editorials/amerman/2008/0917.html on my home page, not because I want to, and not because it is well written. But it pretty well explains the degree of risk that the financial community has created by credit default insurance. Unlike MBS, there are no assets, no income stream, no regulated reserves, just a promise that money will magically appear right when the economy runs out of money.
But before we tar and feather those insurers, let's properly assign blame where it belongs: the Fed and its creators, FDR (created moral hazards in Fannie and Freddie), Burns, Greenspan, Bernanke and all the apologists for the credit-based economy who can see no wrong with creating multiple dollars of debt for every dollar of GDP. Here's another link with the numbers for the hole we've dug (50 trillion in debt - see table L.1 against a 14 trillion GDP): http://www.federalreserve.gov/releases/z1/Current/z1.pdf This level of debt cannot be paid off (think about the proportion of GDP that would be needed, it would eat up the money needed for startups, R&D, etc). The only choices are default (what is looming today) or inflation.
Mar 24, 2007: Here's my web page with what I see as perpetuated myths of global warming: http://shpud.com/myths.html When you find errors, please ping or email. I have already been taken to the woodshed for some and I appreciate the patience of the readers who corrected what I had muddled.
Dec 14, 2003. We've captured Saddam! A big congratulations to our military. Many have sacrificed a lot including their lives to achieve this and I will always remember them.
This is a perfect opportunity to switch to the Afghanistan strategy: a few well protected bases and special forces missions to eliminate specific threats. If the the vast majority of Iraqis want freedom and democracy then they can earn it by keeping the peace, turning in the remaining radicals and building their own government.
Nation-building is mostly liberalism: handouts, price controls, political correctness, and a religious belief in changing people from the top down. We have given the Iraqis the foundation to build a nation, but we can't give them a functioning country, they have to do that themselves