In partnership with our parent organization, the International Center for Journalists (ICFJ), IJNet is connecting journalists with health experts and newsroom leaders through a webinar series on COVID-19. The series is part of the ICFJ Global Health Crisis Reporting Forum.
This article is part of our online coverage of reporting on COVID-19. To see more resources, click here.
During the pandemic, research has pointed to the likelihood that aerosols — made up of tiny droplets of water even smaller than those from a cough — may carry SARS-CoV-2, the novel coronavirus that causes COVID-19. Because aerosols can linger in the air in enclosed spaces, this research has important implications for prevention. But until July 7, the World Health Organization had declined to acknowledge that aerosol-borne particles could transmit the virus.
“There has been a lot of misinformation flying around,” said Columbia University virologist Dr. Angela Rasmussen during an ICFJ webinar this week moderated by ICFJ Senior Vice President Sharon Moshavi. “For better or for worse, the WHO’s motivation has been to not say anything until they're absolutely 100% sure.”
Rasmussen was one of more than 100 scientists who urged the WHO to acknowledge the science on aerosols. “I think that the way we communicate this type of information does need to change, allowing the WHO to potentially make actionable guidance faster,” she said.
Larger droplets produced when people speak or cough will fall to the ground quickly, making a social distance of about six feet (about 1.8 meters) an effective prevention measure. But in aerosols, the virus can linger longer in the air, the scientists wrote, especially in indoor spaces that are poorly ventilated.
Awareness of aerosol transmission highlights the importance of good ventilation and of wearing masks indoors. Aerosols “can remain in the air for a long time, and you could inhale them and become infected,” Rasmussen said.
There’s a “continuum of different-sized particles that you produce when you speak, when you cough, when you are singing, anytime you're really breathing or vocalizing through your mouth,” she said. “Regardless of the particle size, if you're inhaling something out of the air and getting infected from it, that is really airborne transmission.”
Here are additional key quotes from the discussion:
On whether the virus spreads through air conditioning and HVAC systems
The smallest droplets, called particle aerosols, or droplet nuclei, can remain suspended for hours at a time, but appear to be less likely to spread the virus, Rasmussen said. “In general, we don't have any evidence that any large case clusters have been transmitted by, for example, [particles] going through an air conditioning system or an HVAC system.”
Most of the largest respiratory droplets fall quickly to the ground, but “medium-sized droplets can remain in the air for a little bit longer. And we are seeing cases where people are getting infected probably through inhalation of these respiratory droplets,” she said. These “are the primary driver of transmission,” she said.
On why she is less concerned about transmission via surfaces than through the air
Fomite transmission, or indirect person-to-person transmission via surfaces, does not appear to be a major driver of cases, Rasmussen said, but scientists haven’t yet ruled it out. “I think that means you should still consider disinfecting high-touch surfaces, and why I tell people to continue practicing good hand hygiene, because that's really one of the keys to reducing fomite transmission.”
On whether children are susceptible to the virus
“The evidence is somewhat conflicting. Some studies have found that children don't transmit as easily. Others have found that they do. A recent study this past week showed that children did have infectious virus in their respiratory passages. Previous studies have showed that among German children, they had the same distribution of viral loads as adults,” including high-risk adults,” she said. “So children can definitely get infected.”
“It may be that children are in general less susceptible to it themselves and therefore they're not making as much virus and therefore it's harder for them to transmit. It could be some other thing that makes it just that they're not shedding as much virus,” she said. “That's a big open question.”
On whether children should return to school
“I've really been struggling with how safe it is to open schools and not just for the children, but for the staff and for the people in their families. And it's really there are so many unknowns. It's going to be a really tricky thing to balance the needs of those kids that are not virology-related with the needs of the rest of society based on an incomplete set of evidence.”
On herd immunity
Rasmussen believes the term “herd immunity” has been misused during the pandemic. Previously, “herd immunity has been discussed in the context of vaccines only. We've never really reached herd immunity with endemic diseases,” she said. “Smallpox was something that infected people all over the world for millennia. We never reached herd immunity against smallpox. It was only when we had a vaccine that we were able to successfully achieve herd immunity globally and eradicate the virus.”
“In Sweden, where they've attempted this, it hasn't even really provided much of an economic benefit either,” she said. “So I think people really need to consider what they're asking people to do when they're saying, ‘Oh, we can get herd immunity by just letting everybody get infected.’"
On why public health officials were slow to recommend that people wear masks
“We didn’t have the same body of evidence in March that we have now about inhaled droplet transmission,” she said. “In early March, a paper came out that showed that masks actually can reduce at least droplet production.”
“I think that the guidance from both the [Centers for Disease Control] and the WHO was intended to preserve personal protective equipment for frontline health care workers.”
Today, “there is enough evidence to suggest that masks may be protective and therefore we should all adopt them,” she said.
“I always wear a mask in a public place at the very least,” she said. “But I don't relax any of my other precautions that I take against transmission. So I continue to physically distance and limit my excursions to essential errands and things like that.”
On whether cotton masks protect the person wearing it or those nearby
“A lot of this has to do with the size of these droplets and the fact that they are made out of water, mostly. So if you are exhaling into the mask, those droplets are getting caught very close to your face,” Rasmussen said. “And any virus that is on those is presumably going to stick to the fibers of the mask that it is exposed to. If you are wearing that same mask and somebody breathes at you, and the respiratory droplets get stuck to the outside of the mask. Eventually, the water in those droplets will start to evaporate and that mask is not super tight.”
She compared a virus passing through the weave of a mask to “a golf ball going through a chain link fence. Eventually, if those droplets evaporate enough, that will be small enough that you could potentially inhale that. But the reality is, we don't actually know what the risk is. We can't really assign percentages,” she said.
On why more research is needed
“We don't entirely know all the different types of tissues and cells in the body that it infects,” she said. “This virus produces a really extreme range of symptoms. Some people have completely asymptomatic infection or at least a very, very mild infection. And some people die of all these really diverse syndromes.”
On her advice for journalists covering COVID-19
“I can't give my opinion on something I don't know anything about because we've seen how this type of misinformation can be extremely harmful,” she said. “If your editor’s bugging you to get something out, don't get something out if it's not complete. If you aren't sure that you're publishing something that communicates the story in a correct way, push back and try to just seek out experts.”
If a source isn’t an expert in a particular area, “ask them if they can recommend somebody who is. So that way, you know, you're talking to independent experts who are not involved with the study or the press release that you're reporting on, so you have some independent expert perspective on that. And I think that really goes a long way to help put it into context for the general public.”
“It’s helpful for me to to understand things that are outside of my subject matter expertise by even just seeking out epidemiologists on Twitter or health economists or anthropologists or people who are in really different fields than me, who can help me understand a complex issue.”