"A new analysis of 172 studies, funded by the World Health Organization, confirms what scientists have said for months: N95 and other respirator masks are far superior to surgical or cloth masks in protecting essential medical workers against the coronavirus.
“It’s been disappointing that both the W.H.O. and the C.D.C. have suggested that surgical masks are adequate, and they’re clearly not,” said David Michaels, a professor at George Washington University who headed the Occupational Safety and Health Administration under President Obama.
“Reliance on surgical masks has no doubt led to many workers being infected,” he said.
N95 masks offered 96 percent protection, the analysis found, while the figure for surgical masks was 77 percent. The findings are particularly important as the United States moves to reopen the economy, Dr. Michaels said.
Workers in health care settings are not the only ones at high risk of coronavirus infection: employees in meatpacking plants and some farms are all also at high risk of coronavirus infection and could benefit from N95 masks, he said.
The new analysis also suggests that covering the eyes with face shields, goggles and glasses may provide additional safeguards for health care workers and people in the community.
The report is among the first to lay out evidence specific to coronaviruses, rather than extrapolating from data on other respiratory viruses.
The coronavirus is thought to spread primarily through droplets expelled when an infected person coughs, sneezes, sings, talks or even breathes. Some infections may also be caused by people touching a contaminated surface and then their mouth, nose or eyes.
Study after study has indicated that the virus can also spread via tiny droplets less than 5 microns, called aerosols. (A micron equals one millionth of a meter.)
But the W.H.O. has so far not acknowledged this risk and has not backed the universal use of masks. “There’s this fear around saying airborne — but that’s what it is,” Dr. MacIntyre said.
A recent review in the journal Science took direct aim at the W.H.O.’s reluctance on this issue, saying the organization’s recommendations for physical distancing and hand washing were based on studies “carried out in the 1930s.”
N95 masks were inexpensive to produce and that other countries, including Australia, had repurposed existing manufacturing facilities to make the masks.
Standing more than three feet away cuts the risk of transmission to 3 percent from 13 percent, the analysis found. Use of masks reduces the odds of infection to 3 percent from 17 percent, and eye protection to 6 percent from 16 percent.
The researchers emphasized that people should also continue to wash their hands frequently.
The review also offers some practical information for disease models. For example, it suggests that contact tracing for people who are potentially exposed should include anyone who has been within six feet of an infected person."
Below are shown the N95 masks in Abu Dhabi ready to be sterilized using UV light. Sun light is perfectly OK for this even coming through the clouds.
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