- We continue to see more and more conclusive proof that the novel coronavirus spreads through the air.
- Airborne COVID-19 transmission happens via tiny droplets and aerosols that infected people expel when coughing, sneezing, yelling, or even just talking normally.
- A new study shows that coronavirus aerosols include the live virus that can infect and multiply in cells, and it proves the pathogen can travel through the air much farther than the six-foot recommendation for social distancing.
It’s not just when we cough and sneeze that we eject invisible projectile out our mouths that can contain pathogens like the novel coronavirus. It also happens when yell, sing, or even just talk normally. But there’s a huge difference between the types, sizes, and behavior of these droplets. Coughing and sneezing projects larger droplets that generally land on the ground within six feet of the infected person, as gravity pulls them downward. But the microdroplets that emerge during talking are much smaller and their water content can evaporate quickly, turning them into aerosols. The aerosols can then move freely in the air, linger for longer periods of time, and travel much farther than the six feet we’ve all been told.
More than 200 scientists urged the World Health Organization (WHO) a few weeks ago to acknowledge the aerosol transmission of COVID-19. The organization finally did it but maintained that it’s droplet transmission that is the main way COVID-19 spreads. Since then, we’ve seen an increasing number of studies that prove the worst thing about the novel coronavirus: The virus does end up suspended in aerosols, and these aerosols are highly infectious.
Scientists from the University of Nebraska were able to collect virus samples from the air in hospital rooms and showed that some of the aerosols had live virus that could replicate inside cells. A different study that looked at the Diamond Princess coronavirus outbreak from early February concluded that airborne transmission was a significant factor of COVID-19 spread aboard the ship. Finally, a separate study showed that tall people might be at a greater risk of contracting the illness, and airborne transmission is the only thing that can explain the phenomenon.
This brings us to the latest research on the matter, a study from the University of Florida that showed not only that the virus in aerosols is infectious, but it can spread through the air well beyond the six feet that authorities keep mentioning as a safe distance.
Researchers invented a new method for capturing aerosols from the air, which could be better than alternatives. Per The New York Times, they have a sampler that uses pure water vapor to enlarge the aerosols so they can be collected from the air. Then the equipment transfers them into a liquid that’s rich with salts, sugar, and protein.
Using the device, the researchers collected samples from a room in a COVID-19 ward at the University of Florida Health Shands Hospital. Neither patient in the room was subject to any medical procedure that could generate aerosols. The WHO and others say that would be the primary source of airborne transmission in a hospital.
The samplers were placed at about seven feet and 16 feet from the patients, and both of them collected infectious virus samples in a dish. The researchers found that the genome sequence of the isolated virus was identical to the one from a swab from a newly admitted asymptomatic patient in the room.
Of note, the room was fitted with efficient air filters and ultraviolet irradiation that should inactivate the virus before the air is reintroduced into the room. That may be why the researchers only found 74 virus particles per liter of air.
If this isn't a smoking gun, then I don't know what is. Successful isolation (cytopathic effect) of SARS-CoV-2 in aerosols collected 2-5 m from patients, genome identical to NP swab, TCID50:genome copies close to 1:1! /1 https://t.co/OJ7jo2P2a0
— Linsey Marr (@linseymarr) August 6, 2020
That’s definitive proof that aerosolized virus is still viable, and that it can travel well over six feet. What no study has figured out is the amount of virus in the aerosol that would need to be inhaled in order to induce an infection. But the findings are relevant for managing the pandemic, especially when it comes to indoor activities and reopening schools. Places that lack proper ventilation could have an increased amount of coronavirus aerosols floating in the air.
The Times points out one oddity in this research. The scientists found as much viral RNA as they did infectious virus. Other methods discovered 100 times more genetic matter than the viral load. As with other coronavirus studies, more research may be required to verify the findings. And this one hasn’t been peer-reviewed at the time of this writing.
But other experts agree that the conclusions are important. “This is what people have been clamoring for,” Dr. Linsey Marr said. “It’s unambiguous evidence that there is infectious virus in aerosols.” Marr is an expert in airborne virus spread but was not involved in the research.
Columbia University virologist Angela Rasmussen told The Times that while she wasn’t sure the amount of virus in that hospital room is “high enough to cause an infection,” the conclusion that you can culture viable virus out of the air is “not a small thing.”
The full study is available at this link.