Is COVID-19 airborne?

We all know that if someone with COVID-19 coughs on us, we might catch the disease. But what if we have a conversation with an infected person, or sit in the same restaurant, or pass them on the street?

More than 239 experts tackled that topic in a letter published on July 6 in the journal Clinical Infectious Diseases. The experts claim the coronavirus likely can travel through airborne microdroplets or aerosols and urge the World Health Organization to tailor its recommendations to account for this type of spread. The letter is just the latest in an ongoing debate about how easily the virus moves from person to person.

Experts have said COVID-19 spreads through droplets when an infected person coughs or sneezes. Infected droplets of that size only travel up to 4 feet before falling to the ground, which is why health experts recommend maintaining 6 feet of social distance. But airborne or aerosol spread refers to much tinier droplets that can linger in the air for hours.

The letter’s writers point out that similar viruses spread this way. A 2004 study suggested that the virus that causes severe acute respiratory syndrome, or SARS, spreads through the air. The experts believe COVID-19 behaves similarly.

The letter also describes specific cases that only seem possible if COVID-19 can spread through aerosols. In early March, 53 of 61 members of a chorale contracted the disease at a rehearsal. In another example, three people became ill after eating in the same restaurant even though video records showed they had no contact with each other.

The experts recommend stricter precautions like bringing air in from outside rather than recirculating air inside public buildings, workplaces, schools, hospitals, and elder care facilities. They also suggest revamping ventilation systems to include high-efficiency air filtration and germ-killing ultraviolet lights. And they think the government officials should further restrict public gatherings.

But some epidemiologists insist there is no clear scientific evidence that COVID-19 spreads through aerosols. And even if it can, such transmission likely happens only in isolated cases.

“It is a shame that they felt the need to publish,” Paul Hunter, a member of the WHO’s infection prevention committee, told Live Science. “Given the ample evidence that reducing droplet transmission works [to reduce COVID-19 spread], throwing other things into the mix only confuses people.”

He added that many of the professionals who signed the letter are not infectious disease experts and don’t fully understand the spread of viruses: “Most of them are chemists, engineers, owners of ventilation companies. They do not have a broad understanding of disease transmission mechanisms. … This issue is more nuanced than many of them realize.”

Treatment front-runner

In the race to develop a treatment for COVID-19, Gilead Sciences may have come up with a winner with remdesivir. In a study conducted by Vanderbilt University Medical Center, the University of North Carolina at Chapel Hill, and Gilead, researchers found the experimental drug inhibited the coronavirus in human lung cell cultures in the lab. Their results also showed it improved lung function in mice infected with the disease.

Since January, doctors have prescribed remdesivir to hospitalized COVID-19 patients when few other options were available. The drug has undergone clinical trials since February, and preliminary reports indicated it may help patients recover more quickly. But researchers still need more thorough preclinical and laboratory evidence of its effectiveness.

“All of the results with remdesivir have been very encouraging, even more so than we would have hoped,” said Vanderbilt research assistant and study co-author Andrea Pruijssers, “but it is still investigational, so it was important to directly demonstrate its activity against SARS-CoV-2 in the lab and in an animal model of disease.”

Further research will focus on remdesivir’s effects at various stages of the disease and in combination with other drugs. Other studies suggest it may help to fight a variety of coronaviruses that could jump to humans in the future.

“We hope that will never happen, but just as we were working to characterize remdesivir over the past six years to be ready for a virus like SARS-CoV-2, we are working and investing now to prepare for any future coronavirus,” Mark Denison, a researcher at Vanderbilt, said. “We want remdesivir and other drugs to be useful both now and in the future.”

Researchers will need to closely monitor whether patients develop liver damage—a rare but severe side effect of remdesivir, according to a Medscape article published on July 8. —J.B.

Catching COVID-19

Scientists at the University of Houston collaborated with Medistar, a Houston-based medical real estate development firm, to design an air filter that can trap and kill the virus that causes COVID-19.

Researchers found that 99.8 percent of the aerosolized virus died after passing once through a filter made from nickel foam and heated to nearly 400 degrees Fahrenheit, according to a paper published on July 7 in Materials Today Physics.

Nickel foam is flexible and porous, allowing good airflow, and it’s easy to heat because it can conduct electricity. Rather than using an external heat source, the scientists folded the material and connected multiple compartments with electrical wires, minimizing the amount of heat that could escape.

“This filter could be useful in airports and in airplanes, in office buildings, schools and cruise ships to stop the spread of COVID-19,” the paper’s co-author Zhifeng Ren said.

Medistar wants to first make the device available to schools, healthcare facilities, public transit, and other places with essential workers. The company also hopes it can get nonessential workers back to public workspaces safely and has proposed a desktop model for offices. —J.B.

Stargazers’ treat

The brightest comet visible from the Northern Hemisphere in the past quarter century is due to streak past Earth. It’s closest approach should occur in about one week, and it will remain visible until mid-August.

The newly discovered Comet Neowise shot through Mercury’s orbit at the beginning of this month. Its close brush with the sun caused dust and gas to burn off its surface and enlarge its fiery tail.

The comet measures about 3 miles in diameter and will be visible to the naked eye in areas without light pollution. But you will need binoculars to see its impressive tail. —J.B.