https://www.nature.com/articles/d41586-020-00974-w
EXCERPT: . . . But experts that work on airborne respiratory illnesses and aerosols say that gathering unequivocal evidence for airborne transmission could take years and cost lives. We shouldn’t “let perfect be the enemy of convincing”, says Michael Osterholm, an infectious-disease epidemiologist at the University of Minnesota in Minneapolis.
“In the mind of scientists working on this, there’s absolutely no doubt that the virus spreads in the air,” says aerosol scientist Lidia Morawska at the Queensland University of Technology in Brisbane, Australia. “This is a no-brainer.”
When public health officials say there isn't sufficient evidence to say that COVID-19 is airborne, they specifically mean transported in virus-laden aerosols smaller than 5 micrometres in diameter. Compared with droplets, which are heftier and thought to travel only short distances after someone coughs or sneezes before falling to the floor or onto other surfaces, aerosols can linger in the air for longer and travel further.
Most transmission occurs at close range, says Ben Cowling, an epidemiologist at the University of Hong Kong. But the distinction between droplets and aerosols is unhelpful because “the particles that come out with virus can be a wide range of sizes. Very, very large ones right down to aerosols”, he says. And if SARS-CoV-2 is transmitting in aerosols, it is possible that virus particles can build up over time in enclosed spaces or be transmitted over greater distances.
Aerosols are also more likely to be produced by talking and breathing, which might even constitute a bigger risk than sneezing and coughing, says virologist Julian Tang at the University of Leicester, UK. “When someone’s coughing, they turn away, and when they’re sneezing, they turn away,” he says. That’s not the case when we talk and breathe.
A study of people with influenza found that 39% of people exhaled infectious aerosols. As long as we are sharing an airspace with someone else, breathing in the air that they exhale, airborne transmission is possible, says Tang.
[...] Whatever the infectious dose, length of exposure is probably an important factor too, says Tang. Each breath might not produce much virus, he says, but “if you’re standing beside [someone who’s infected], sharing the same airspace with them for 45 minutes, you’re going to inhale enough virus to cause infection”.
But capturing those small concentrations of aerosols that, given the right combination of airflow, humidity and temperature, might build to an infectious dose over time, is “extremely difficult”, says Morawska. “We could say that we need more data, but then we should acknowledge the difficulty of collecting the data,” she says... (MORE - details)
RELATED: Just breathing or talking may be enough to spread COVID-19 after all
EXCERPT: . . . But experts that work on airborne respiratory illnesses and aerosols say that gathering unequivocal evidence for airborne transmission could take years and cost lives. We shouldn’t “let perfect be the enemy of convincing”, says Michael Osterholm, an infectious-disease epidemiologist at the University of Minnesota in Minneapolis.
“In the mind of scientists working on this, there’s absolutely no doubt that the virus spreads in the air,” says aerosol scientist Lidia Morawska at the Queensland University of Technology in Brisbane, Australia. “This is a no-brainer.”
When public health officials say there isn't sufficient evidence to say that COVID-19 is airborne, they specifically mean transported in virus-laden aerosols smaller than 5 micrometres in diameter. Compared with droplets, which are heftier and thought to travel only short distances after someone coughs or sneezes before falling to the floor or onto other surfaces, aerosols can linger in the air for longer and travel further.
Most transmission occurs at close range, says Ben Cowling, an epidemiologist at the University of Hong Kong. But the distinction between droplets and aerosols is unhelpful because “the particles that come out with virus can be a wide range of sizes. Very, very large ones right down to aerosols”, he says. And if SARS-CoV-2 is transmitting in aerosols, it is possible that virus particles can build up over time in enclosed spaces or be transmitted over greater distances.
Aerosols are also more likely to be produced by talking and breathing, which might even constitute a bigger risk than sneezing and coughing, says virologist Julian Tang at the University of Leicester, UK. “When someone’s coughing, they turn away, and when they’re sneezing, they turn away,” he says. That’s not the case when we talk and breathe.
A study of people with influenza found that 39% of people exhaled infectious aerosols. As long as we are sharing an airspace with someone else, breathing in the air that they exhale, airborne transmission is possible, says Tang.
[...] Whatever the infectious dose, length of exposure is probably an important factor too, says Tang. Each breath might not produce much virus, he says, but “if you’re standing beside [someone who’s infected], sharing the same airspace with them for 45 minutes, you’re going to inhale enough virus to cause infection”.
But capturing those small concentrations of aerosols that, given the right combination of airflow, humidity and temperature, might build to an infectious dose over time, is “extremely difficult”, says Morawska. “We could say that we need more data, but then we should acknowledge the difficulty of collecting the data,” she says... (MORE - details)
RELATED: Just breathing or talking may be enough to spread COVID-19 after all