is a national expert on respiratory protection and infectious diseases and a research consultant with the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota (UMN). Dr MacIntyre is Professor of Global Security at the University of New South Wales. She coauthored a separate critique of the Jefferson Cochrane review. Dr Ulrich is a UMN assistant professor in the Division of Environmental Health Sciences and a CIDRAP researcher. Dr Osterholm is CIDRAP director and Regents Professor at UMN.
Two recent publications conclude there are no differences between surgical masks and respirators for preventing person-to-person transmission of infectious respiratory viruses like SARS-CoV-2 and influenza. But these studies are deeply flawed.
One of these is a randomized controlled trial (RCT) by Loeb et al comparing SARS-CoV-2 infections in healthcare workers wearing respirators or masks for care of COVID-19 patients.1 The other is a Cochrane review by Jefferson et al of mask and respirator studies in households and healthcare settings.2
Both are built on the premise that infectious respiratory viruses like SARS-CoV, SARS-CoV-2, MERS-CoV, and influenza are only transmitted person to person by large droplets. This is not true. The science is very clear that the predominant mode by which these viruses are transmitted person to person is inhalation of small particles, most of which are around 1 micrometer.3–13
COVID-19 and flu are spread by aerosol inhalation
Droplet transmission occurs when someone coughs or sneezes into the eyes, nose, or mouth of someone nearby. This might happen when a healthcare provider is in close contact with a symptomatic person and perhaps when parents are caring for sick children, but otherwise this is a fairly unlikely event.14
People continuously release many particles in a wide range of sizes but most of them are relatively small (around 1 micrometer), when they’re breathing, talking, singing—and coughing or sneezing. The smaller particles remain suspended in air for long periods—minutes to hours—and can accumulate over time and easily disperse throughout an indoor space. Numerically, breathing and talking contribute much more than coughing or sneezing to the amount of virus in the air because they occur continuously or very frequently.
SARS-CoV-2 is capable of remaining viable in air for some hours. We know that people with COVID-19 are most infectious just before and as symptoms are developing, so transmission is possible before anyone knows they’re infected. Some 30% or more of infected people never develop symptoms but are still infectious.
All of these facts explain why aerosol inhalation is much more likely than droplet transmission. They also explain why infection can occur both near and far from an infected source.
Masks offer little protection
We’ve discussed cloth and surgical masks in detail elsewhere (see «Masks-for-all for COVID-19 not based on sound data» and «What can masks do?» part 1). The most important variables are filter efficiency—how well the filter collects particles of all sizes; fit—how well the facepiece prevents leakage around the edges; and breathing resistance—how easy it is to inhale and exhale through the filter.
Some surgical masks have a reasonable filter but exhibit increased particle leakage around the edges because of their loose fit. Without a close fit around the face, a surgical mask cannot limit inward or outward leakage of particles as well as a respirator can.
Surgical masks vary widely in filter material, design, and effectiveness, but most don’t have high filter efficiency. The filter tests required by the US Food and Drug Administration are not predictive of surgical mask filter performance, so it’s impossible to know which surgical mask filters can collect small particles.15,16 Surgical masks are not expected to fit tightly against the face, so they have considerable inward and outward leakage of particles.
A surgical mask might prevent large droplets from contacting the nose and mouth but offers no protection from someone else’s smaller inhalable particles. And it will not prevent such particles from being emitted around the edge of the mask.
A surgical mask might prevent large droplets from contacting the nose and mouth but offers no protection from someone else’s smaller inhalable particles.
Cloth is not designed to collect particles and has a very low collection efficiency for smaller particles and thus offers little protection for the wearer or nearby people. It’s possible to make a cloth mask more efficient by increasing the thickness or number of layers, but that will also increase the breathing resistance, which decreases comfort.
Respirators prevent aerosol inhalation
Respirators are not masks. The correct term for a device approved by the National Institute for Occupational Safety and Health (NIOSH) to prevent inhalation of hazardous materials is «respirator» (and not «respirator mask»).
Respirators have very effective filters and are designed to fit most faces. A respirator filter is easy to breathe through, because it’s made of a fibrous electret material that has low breathing resistance. Any type of respirator filter approved by NIOSH—N, P, R, 95, 99, 100—will be effective at collecting human-generated aerosols.
Although designed to protect the wearer from inhaling hazardous aerosols, an N95 filtering facepiece respirator (FFR) will also prevent the outward leakage of particles produced by the wearer when breathing, talking, singing, etc.17,18
FAA investigating contact between 2 United airplanes on Boston Logan tarmac
The Federal Aviation Administration is investigating a Monday incident between two United Airlines flights at Boston Logan International Airport, the agency said in a statement to CNN.
“As a tow tug was pushing it back from the gate at Boston Logan International Airport, the right wing of United Airlines Flight 515 struck the tail of United Airlines Flight 267 around 8:30 a.m. local time this morning,” the FAA statement said.
“Both aircraft were Boeing 737s that were scheduled for departure,” the statement added.
has reached out to United Airlines and Massport for more information about the incident.
A sudden jolt’
Passenger Nicholas Leone took a photo after the incident and described to CNN what happened.
“I felt a sudden jolt and look to my right to see that the plane had crashed into the still plane, ” he said. “After seeing the fire trucks and police cars, people were a little rattled. Thankfully everyone was able to offboard quickly.”
Passengers said the incident was a little jarring, according to CNN affiliate WHDH in Boston.
“It was just a pretty big shake,” said passenger Martin Neusch. “While we were on the plane, it just clipped the wings, so the two wings clipped each other on the plane.”
The station said passengers on both planes were rebooked on other flights set for Monday afternoon.
The contact between two aircraft on Monday morning follows a string of five close-call incidents earlier this year, including one at Boston Logan last week.
Air traffic controllers stopped a departing private jet from running into a JetBlue flight as it was coming in to land at Logan last Monday night, according to the FAA.
The FAA and the National Transportation Safety Board are investigating that incident.
The two planes involved came within 565 feet (172 meters) of colliding, according to Flightradar24’s preliminary review of its data.
What’s the safest seat on a plane?. Travel asked an aviation expert
The NTSB is also investigating four other runway incursions involving commercial airliners at major US airports this year.
It’s investigating a possible “runway incursion” in Burbank, California, involving Mesa and SkyWest regional airliners.
Three other incidents have occurred at Honolulu, Austin and New York’s JFK airport this year.
Flambéed pizza thought to have sparked deadly Madrid restaurant fire
A fire believed to have been started by a flambéed pizza has killed two people and injured 12 others at a restaurant in the Spanish capital Madrid, city officials said Saturday.
“It appears the fire started when a flambéed pizza was being served, which set fire to the decorations in the restaurant,” Madrid Mayor Jose Luis Martinez Almeida told Spain’s state television TVE at the scene on Saturday, hours after the late Friday night blaze.
Spanish media reported that a specialty of the restaurant was a pizza in the flambé style – a cooking procedure where spirits are poured on the food and briefly set alight.
“Firefighters told me it was a ferocious fire in the way it started and the smoke it generated, and if the fire station wasn’t just 100 meters (around 330 feet) away, the number of fatalities could have been higher,” said Almeida, speaking to TVE.
Carlos Marin, a Madrid fire department night supervisor, said the restaurant “had just one exit, and since the fire was very close to the door, people went back to the rear of the restaurant, and they were completely trapped,” in videos tweeted by Madrid city emergency services.
The fire was quickly extinguished. Firefighters pulled 12 injured people from the restaurant, and six were taken to a hospital. That was in addition to the two fatalities, said Montse Marcos, a supervisor with the Madrid city ambulance services.
The fire was in the Plaza de Manuel Becerra, on the edge of the Spanish capital’s upscale Salamanca neighborhood.
As Ukraine prepares counteroffensive, Russia appears in disarray
Ukraine’s much-anticipated counteroffensive appears imminent – and the way each side is preparing speaks volumes about their readiness.
Kyiv’s front lines are abuzz with vehicle movement and artillery strikes, with regular explosions hitting vital Russian targets in occupied areas.
Its defense minister has said preparations are “coming to an end” and President Volodymyr Zelensky has assured a counteroffensive “will happen,” while demurring on any exact start date.
It may have already started; it may be weeks away. We don’t know – and that fact is a strong measure of Ukraine’s success as this begins.
Moscow, on the other hand, is in the closing-time bar brawl stage of their war. After losing Kharkiv and Kherson, they have had at least seven months to ready the next likely target of Ukrainian attack: Zaporizhzhia.
That has happened, with vast trench defense networks that can be seen from space. That recognition of their enormity is not necessarily a compliment in 2023. They are big, yes, but they are also something anyone can peruse on Google. That’s not great in an era of precise rockets and speedy armored advances.
But it’s the last 72 hours that have perhaps most betrayed Russia’s lacking readiness.
First, the apparent firing of the deputy defense minister in charge of logistics, Mikhail Mizintsev. The Russian Ministry of Defense has not spelled out his dismissal, merely issuing a decree that Aleksey Kuzmenkov now has his job.
(A caveat: Prigozhin is not the most trustworthy source, and provides little evidence for what he says. But this sort of public spat isn’t something Moscow would encourage at this sensitive moment).
Russia’s eroding ammunition supplies were long known, but to suggest imminent failure just ahead of the counteroffensive smacks of a major bid to shift blame.
The bottom line is, the hours before Ukraine moves are shrinking. The amount we know about their emotional state, or target, is almost zero. And the extent of Moscow’s internal indecision, rivalries and disunity only grows.
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