Tiny airborne particles may pose a big coronavirus problem

NEW YORK — At a University of Maryland lab, people infected with the new coronavirus take turns sitting in a chair and putting their faces into the big end of a large cone. They recite the alphabet and sing or just sit quietly for a half hour. Sometimes they cough.

The cone sucks up everything that comes out of their mouths and noses. It’s part of a device called “Gesundheit II” that is helping scientists study a big question: Just how does the virus that causes COVID-19 spread from one person to another?

It clearly hitchhikes on small liquid particles sprayed out by an infected person. People expel particles while coughing, sneezing, singing, shouting, talking and even breathing. But the drops come in a wide range of sizes, and scientists are trying to pin down how risky the various kinds are.

The answer affects what we should all be doing to avoid getting sick. That’s why it was thrust into headlines a few days ago when a U.S. health agency appeared to have shifted its position on the issue, but later said it had published new language in error.

The recommendation to stay at least 6 feet (2 metres) apart — some authorities cite about half that distance — is based on the idea that larger particles fall to the ground before they can travel very far. They are like the droplets in a spritz of a window cleaner, and they can infect somebody by landing on their nose, mouth or eyes, or maybe being inhaled.

But some scientists are now focusing on tinier particles, the ones that spread more like cigarette smoke. Those are carried by wisps of air and even upward drafts caused by the warmth of our bodies. They can linger in the air for minutes to hours, spreading throughout a room and build up if ventilation is poor.

The potential risk comes from inhaling them. Measles can spread this way, but the new coronavirus is far less contagious than that.

For these particles, called aerosols, “6 feet is not a magic distance,’’ says Linsey Marr, a leading researcher who is studying them at Virginia Tech in Blacksburg. But she says it’s still important to keep one’s distance from others, “the farther the better,” because aerosols are most concentrated near a source and pose a bigger risk at close range.

Public health agencies have generally focused on the larger particles for coronavirus. That prompted more than 200 other scientists to publish a plea in July to pay attention to the potential risk from aerosols. The World Health Organization, which had long dismissed a danger from aerosols except in the case of certain medical procedures, later said that aerosol transmission of the coronavirus can’t be ruled out in cases of infection within crowded and poorly ventilated indoor spaces.

The issue drew attention recently when the U.S. Centers for Disease Control and Prevention posted and then deleted statements on its website that highlighted the idea of aerosol spread. The agency said the posting was an error, and that the statements were just a draft of proposed changes to its recommendations.

Dr. Jay Butler, CDC’s deputy director for infectious disease, told The Associated Press that the agency continues to believe larger and heavier droplets that come from coughing or sneezing are the primary means of transmission.

Last month Butler told a scientific meeting that current research suggests aerosol spreading of the coronavirus is possible but it doesn’t seem to be the main way that people get infected. Further research may change that conclusion, he added, and he urged scientists to study how often aerosol spread of the coronavirus occurs, what situations make it more likely and what reasonable steps might prevent it.

Marr said she thinks infection by aerosols is “happening a lot more than people initially were willing to think.”

As a key piece of evidence, Marr and others point to so-called “superspreader” events where one infected person evidently passed the virus to many others in a single setting.

In March, for example, after a choir member with coronavirus symptoms attended a rehearsal in Washington state, 52 others who had been seated throughout the room were found to be infected and two died. In a crowded and poorly ventilated restaurant in China in January, the virus evidently spread from a lunchtime patron to five people at two adjoining tables in a pattern suggesting aerosols were spread by the air conditioner. Also in January, a passenger on a Chinese bus apparently infected 23 others, many of whom were scattered around the vehicle.

Butler said such events raise concern about aerosol spread but don’t prove it happens.

There could be another way for tiny particles to spread. They may not necessarily come directly from somebody’s mouth or nose, says William Ristenpart of the University of California, Davis. His research found that if paper tissues are seeded with influenza virus and then crumpled, they give off particles that bear the virus. So people emptying a wastebasket with tissues discarded by somebody with COVID-19 should be sure to wear a mask, he said.

Scientists who warn about aerosols say current recommendations still make sense.

Wearing a mask is still important, and make sure it fits snugly. Keep washing those hands diligently. And again, staying farther apart is better than being closer together. Avoid crowds, especially indoors.

Their main addition to recommendations is ventilation to avoid a buildup of aerosol concentration. So, the researchers say, stay out of poorly ventilated rooms. Open windows and doors. One can also use air-purifying devices or virus-inactivating ultraviolet light.

Best of all: Just do as much as you can outdoors, where dilution and the sun’s ultraviolet light work in your favour.

“We know outdoors is the most spectacularly effective measure, by far,’’ says Jose-Luis Jimenez of the University of Colorado-Boulder. “Outdoors it is not impossible to get infected, but it is difficult.”

The various precautions should be used in combination rather than just one at a time, researchers say. In a well ventilated environment, “6 feet (of separation) is pretty good if everybody’s got a mask on” and nobody stays directly downwind of an infected person for very long, says Dr. Donald Milton of the University of Maryland School of Public Health, whose lab houses the Gesundheit II machine.

Duration of exposure is important, so there’s probably not much risk from a short elevator ride while masked or being passed by a jogger on the sidewalk, experts say.

Scientists have published online tools for calculating risk of airborne spread in various settings.

At a recent meeting on aerosols, however, Dr. Georges Benjamin, executive director of the American Public Health Association, noted that preventive steps can be a challenge in the real world. Keeping apart from other people can be difficult in homes that house multiple generations. Some old buildings have windows that were “nailed shut years ago,” he said. And “we have far too many communities where they simply don’t have access to clean water to wash their hands.”

It might seem strange that for all the scientific frenzy to study the new coronavirus, the details of how it spreads can still be in doubt nine months later. But history suggests patience.

“We’ve been studying influenza for 102 years,” says Milton, referring to the 1918 flu epidemic. “We still don’t know how it’s transmitted and what the role of aerosols is.”

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Red Deer Mayor Tara Veer and Roland Gaviola, Iglesia ni Cristo Church of Christ district minister in the Calgary region, stand in front of the 300-plus boxes of donated food at the Red Deer Food Bank Saturday afternoon. (Photo by Sean McIntosh/Advocate staff)
Red Deer Food Bank receives big donation from local church

More than 300 boxes of food were donated Saturday

Jason Aquino has been adding to his front lawn Halloween display for the past five years. “I wanted to do it big this year, because even in the pandemic, we can still enjoy Halloween,” says the Red Deer father.
Halloween spookiness rises to new level

Rare astronomical occurrence caps off a strange holiday

Alberta Health Services' central zone jumped from 162 active COVID-19 cases to 178 on Friday. Five additional deaths were reported provincewide, bringing the toll to 323. THE CANADIAN PRESS/Graham Hughes
622 new COVID-19 cases set another daily high Friday

Province confirmed 622 additional cases Friday

Advocate file photo
Man awaiting murder trial facing two new trials for breaching release conditions

Quentin Strawberry going to trial in March in connection with 2019 murder

Ecole La Prairie students and teachers dressed up in Halloween costumes and paraded by Barrett Kiwanis Place, while waving at the building’s residents in Red Deer on Friday. (Photo by Sean McIntosh/Advocate staff)
Ecole La Prairie students parade in Halloween costumes for Red Deer seniors

Dozens of Red Deer students put on their Halloween costumes to spread… Continue reading

Over the years, Janice Blackie-Goodine’s home in Summerland has featured elaborate Halloween displays and decorations each October. (File photo)
QUIZ: How much do you really know about Halloween?

Oct. 31 is a night of frights. How much do you know about Halloween customs and traditions?

A costumed trick or treater turns after being given candy during Halloween celebrations in Toronto, on Tuesday, October 31, 2017. Families across the country have assembled their costumes and stockpiled their candy to celebrate a Halloween that is -- hopefully -- unlike any other. Public health restrictions to protect against COVID-19 vary depending on the region, but most officials have given trick-or-treating the go-ahead.THE CANADIAN PRESS/Chris Young
Families prepare for pandemic-era Halloween with public health restrictions in place

TORONTO — Canadians may be putting the final touches on their costumes… Continue reading

Indigenous fishermen adjust lines on their boat in Saulnierville, N.S. on Wednesday, Oct. 21, 2020. THE CANADIAN PRESS /Andrew Vaughan
N.S. Mi’kmaq chiefs demand stop of alleged federal plans to seize lobster traps

HALIFAX — The Assembly of Nova Scotia Mi’kmaq Chiefs is alleging the… Continue reading

Grand Chief Arlen Dumas of the Assembly of Manitoba Chiefs speaks in Ottawa on Thursday, December 7, 2017. Dumas says he's concerned about the growing number of COVID-19 cases First Nation communities. THE CANADIAN PRESS/Fred Chartrand
The family of Allan Landrie, shown in a family handout photo, is disappointed the Saskatchewan Coroners Service isn’t considering an inquest into the 72-year-old's hospital death. Landrie's death in September 2019 was ruled a suicide. More than three days had passed before his body was discovered locked in a hospital bathroom in Saskatoon. THE CANADIAN PRESS/HO
‘He was so sick,’ says daughter of Saskatoon man who committed suicide in hospital

Allan Landrie’s body was discovered three days after his death

Supporters listen as Democratic presidential candidate former Vice President Joe Biden speaks at a rally at the Iowa State Fairgrounds in Des Moines, Iowa, Friday, Oct. 30, 2020. (AP Photo/Andrew Harnik)
Obama: Trump failed to take pandemic, presidency seriously

FLINT, Mich. — Calling Joe Biden his “brother,” Barack Obama on Saturday… Continue reading

ll
Imagining the origins of Halloween

Long ago and far away, a small assemblage of English people gathered… Continue reading

Red Deer College president Peter Nunoda. (Photo by contributed)
Peter Nunoda: Winter term will be busier on RDC campus

In my column last month, I shared details about Red Deer College’s… Continue reading

FILE - In this Jan. 23, 1987 file photo, actor Sean Connery holds a rose in his hand as he talks about his new movie "The Name of the Rose" at a news conference in London. Scottish actor Sean Connery, considered by many to have been the best James Bond, has died aged 90, according to an announcement from his family. (AP Photo/Gerald Penny, File)
Actor Sean Connery, the ‘original’ James Bond, dies at 90

He died peacefully in his sleep overnight in the Bahamas

Most Read