"Airborne virus plays a significant role in community transmission, many experts believe. A new study fills in the missing piece: Floating virus can infect cells.
Skeptics of the notion that the coronavirus spreads through the air — including many expert advisers to the World Health Organization — have held out for one missing piece of evidence: proof that floating respiratory droplets called aerosols contain live virus, and not just fragments of genetic material.
Now a team of virologists and aerosol scientists has produced exactly that: confirmation of infectious virus in the air.
“This is what people have been clamoring for,” said Linsey Marr, an expert in airborne spread of viruses who was not involved in the work. “It’s unambiguous evidence that there is infectious virus in aerosols.”
A research team at the University of Florida succeeded in isolating live virus from aerosols collected at a distance of seven to 16 feet from patients hospitalized with Covid-19 — farther than the six feet recommended in social distancing guidelines.
The findings, posted online last week, have not yet been vetted by peer review, but have already caused something of a stir among scientists. “If this isn’t a smoking gun, then I don’t know what is,” Dr. Marr tweeted last week.
But some experts said it still was not clear that the amount of virus recovered was sufficient to cause infection.
The research was exacting. Aerosols are minute by definition, measuring only up to five micrometers across; evaporation can make them even smaller. Attempts to capture these delicate droplets usually damage the virus they contain.
“It’s very hard to sample biological material from the air and have it be viable,” said Shelly Miller, an environmental engineer at the University of Colorado Boulder who studies air quality and airborne diseases.
“We have to be clever about sampling biological material so that it is more similar to how you might inhale it.”
...This time, the team collected air samples from a room in a ward dedicated to Covid-19 patients at the University of Florida Health Shands Hospital. Neither patient in the room was subject to medical procedures known to generate aerosols, which the W.H.O. and others have contended are the primary source of airborne virus in a hospital setting.
...The genome sequence of the isolated virus was identical to that from a swab of a newly admitted symptomatic patient in the room.
...“I’m just not sure that these numbers are high enough to cause an infection in somebody,” said Angela Rasmussen, a virologist at Columbia University in New York.
“The only conclusion I can take from this paper is you can culture viable virus out of the air,” she said. “But that’s not a small thing.”
Several experts noted that the distance at which the team found virus is much farther than the six feet recommended for physical distancing.
“We know that indoors, those distance rules don’t matter anymore,” Dr. Schofield said. It takes about five minutes for small aerosols to traverse the room even in still air, she added.
The six-foot minimum is “misleading, because people think they are protected indoors and they’re really not,” she said.
That recommendation was based on the notion that “large ballistic cannonball-type droplets” were the only vehicles for the virus, Dr. Marr said. The more distance people can maintain, the better, she added.
The findings should also push people to heed precautions for airborne transmission like improved ventilation, said Seema Lakdawala, a respiratory virus expert at the University of Pittsburgh.
“We all know that this virus can transmit by all these modes, but we’re only focusing on a small subset,” Dr. Lakdawala said.
https://www.nytimes.com/2020/08/11/health/coronavirus-aerosols-indoors.html
:smoking:
Skeptics of the notion that the coronavirus spreads through the air — including many expert advisers to the World Health Organization — have held out for one missing piece of evidence: proof that floating respiratory droplets called aerosols contain live virus, and not just fragments of genetic material.
Now a team of virologists and aerosol scientists has produced exactly that: confirmation of infectious virus in the air.
“This is what people have been clamoring for,” said Linsey Marr, an expert in airborne spread of viruses who was not involved in the work. “It’s unambiguous evidence that there is infectious virus in aerosols.”
A research team at the University of Florida succeeded in isolating live virus from aerosols collected at a distance of seven to 16 feet from patients hospitalized with Covid-19 — farther than the six feet recommended in social distancing guidelines.
The findings, posted online last week, have not yet been vetted by peer review, but have already caused something of a stir among scientists. “If this isn’t a smoking gun, then I don’t know what is,” Dr. Marr tweeted last week.
But some experts said it still was not clear that the amount of virus recovered was sufficient to cause infection.
The research was exacting. Aerosols are minute by definition, measuring only up to five micrometers across; evaporation can make them even smaller. Attempts to capture these delicate droplets usually damage the virus they contain.
“It’s very hard to sample biological material from the air and have it be viable,” said Shelly Miller, an environmental engineer at the University of Colorado Boulder who studies air quality and airborne diseases.
“We have to be clever about sampling biological material so that it is more similar to how you might inhale it.”
...This time, the team collected air samples from a room in a ward dedicated to Covid-19 patients at the University of Florida Health Shands Hospital. Neither patient in the room was subject to medical procedures known to generate aerosols, which the W.H.O. and others have contended are the primary source of airborne virus in a hospital setting.
...The genome sequence of the isolated virus was identical to that from a swab of a newly admitted symptomatic patient in the room.
...“I’m just not sure that these numbers are high enough to cause an infection in somebody,” said Angela Rasmussen, a virologist at Columbia University in New York.
“The only conclusion I can take from this paper is you can culture viable virus out of the air,” she said. “But that’s not a small thing.”
Several experts noted that the distance at which the team found virus is much farther than the six feet recommended for physical distancing.
“We know that indoors, those distance rules don’t matter anymore,” Dr. Schofield said. It takes about five minutes for small aerosols to traverse the room even in still air, she added.
The six-foot minimum is “misleading, because people think they are protected indoors and they’re really not,” she said.
That recommendation was based on the notion that “large ballistic cannonball-type droplets” were the only vehicles for the virus, Dr. Marr said. The more distance people can maintain, the better, she added.
The findings should also push people to heed precautions for airborne transmission like improved ventilation, said Seema Lakdawala, a respiratory virus expert at the University of Pittsburgh.
“We all know that this virus can transmit by all these modes, but we’re only focusing on a small subset,” Dr. Lakdawala said.
https://www.nytimes.com/2020/08/11/health/coronavirus-aerosols-indoors.html
:smoking:
