Virus World

A plea issued by 239 scientists from around the world to recognize and mitigate airborne transmission of COVID-19 addressed to international health authorities is to be published in the journal Clinical Infectious Diseases. The 239 signatories from 32 countries come from many different areas of science and engineering, including virology, aerosol physics, flow dynamics, exposure and epidemiology, medicine, and building engineering. Led by internationally recognized air quality and health expert QUT Professor Lidia Morawska, the appeal is to address the overwhelming research finding that an infected person exhales airborne virus droplets when breathing and talking that can travel further than the current 1.5m social distance requirement.

"Studies by the signatories and other scientists have demonstrated beyond any reasonable doubt that viruses are exhaled in microdroplets small enough to remain aloft in the air and pose a risk of exposure beyond 1 to 2m by an infected person," Professor Morawska, director of the International Air Quality and Health Laboratory, said. "At typical indoor air velocities, a 5-micron droplet will travel tens of meters, much greater than the scale of a typical room while settling from a height of 1.5m above the floor." Signatories to the appeal come from many disciplines including different areas of science and engineering, including virology, aerosol physics, flow dynamics, exposure and epidemiology, medicine, and building engineering. "Expertise in many science and engineering areas enables us to understand the characteristics and mechanisms behind the generation of respiratory microdroplets, how viruses survive in these microdroplets, and how airflow patterns carry microdroplets in buildings," Professor Morawska said.

The measures that need to be taken to mitigate airborne transmission include:

• Provide sufficient and effective ventilation (supply clean outdoor air, minimize recirculating air) particularly in public buildings, workplace environments, schools, hospitals, and aged care homes.
• Supplement general ventilation with airborne infection controls such as local exhaust, high efficiency air filtration, and germicidal ultraviolet lights.
• Avoid overcrowding, particularly in public transport and public buildings.

Original letter published in J. Clinical Infect. Diseases (July 6, 2020):

https://doi.org/10.1093/cid/ciaa939

When researcher Josh Santarpia stands at the foot of a bed, taking measurements with a device that can detect tiny, invisible particles of mucus or saliva that come out of someone's mouth and move through the air, he can tell whether the bedridden person is speaking or not just by looking at the read-out on his instrument. "So clearly the particles that that person is putting out are being breathed in by someone that is five feet away from them, at the foot of their bed," says Santarpia, who studies biological aerosols at the University of Nebraska Medical Center. "Do they contain virus? I don't know for sure."

He and his colleagues are doing their best to find out. Already, using another contraption that looks like a fancy dustbuster, they've sucked up air samples from 11 isolation rooms that housed 13 people who tested positive for COVID-19 infection, all of whom had a variety of mild symptoms. In those air samples, researchers found the genetic fingerprint of the virus. "It was more than half of the samples that we took. It was fairly ubiquitous," says Santarpia, "but the concentrations were really pretty low." Finding the genetic material doesn't necessarily mean that there's viable virus that could potentially make someone sick, he cautions. Some preliminary evidence indicates that this might be the case, but the team wants to do more work "and try and be as certain as we possibly can whether or not certain samples had infectious virus in them or not." They want to know that with a high degree of confidence because the question of whether or not the coronavirus can be "airborne" is extremely contentious right now — and it's a question that has real implications for what people should do to avoid getting infected....