We’ve long known about the transmission of the coronavirus via respiratory droplets from coughs and sneezes, which is why everyone is encouraged to wear masks and stay six feet away from each other. The question of airborne spread has been contentious for months, with some scientists arguing for preventive guidance, but public health agencies delayed in recognizing airborne transmission. However, we now know that six feet isn’t far enough to prevent inhalation of aerosolized particles.
This acknowledgement, and the fact it took so long, has led to some confusion about the way the novel coronavirus spreads, reinforcing the need for precautionary measures. Learn what experts have to say about the airborne spread of COVID-19 and what it means for you.
“From what we currently know, the preponderance of the evidence is that transmission is mainly through respiratory droplets and aerosols, with contamination of surfaces playing a limited role in transmission,” says Dr. Davidson Hamer, professor of global health and medicine at the Boston University School of Public Health and School of Medicine.
According to the CDC, the coronavirus mainly spreads through direct and close contact, such as talking to someone without a mask in close quarters. It sometimes spreads through airborne transmission and occasionally spreads through indirect contact, such as touching infected surfaces and then touching your nose, mouth or eyes.
What does it mean when a virus is airborne?
Don’t worry, it’s not like the 1995 movie Outbreak.
Warner Bros. Pictures
According to the World Health Organization, “airborne transmission is defined as the spread of an infectious agent caused by the dissemination of droplet nuclei (aerosols) that remain infectious when suspended in air over long distances and time.”
In other words, when a virus is airborne, it spreads through the air via microscopic particles that can be inhaled.
Dr. Joseph Allen, director of the Healthy Buildings program at Harvard and an assistant professor of exposure assessment science at the T.H. Chan School of Public Health, says the public simply needs to understand that this means our “safe zone” of six feet doesn’t necessarily exist.
“Of course, it’s a bit more nuanced than that,” he says, “but the public has been told that exposure happens within six feet.” The truth is, Allen continues, we generate particles that can travel further than that. And because of their small size, they also stay in the air longer.
We all release particles of all sizes when we sneeze.
Getty Images
This is where the confusion starts, says Dr. Philip Tierno, professor of microbiology and pathology at New York University School of Medicine. The term “respiratory droplets” refers only to where the particles come from. A respiratory droplet — something that comes from your respiratory tract and is expelled from your nose or mouth — can “be micro or macro in size,” Tierno explains.
Every time you sneeze or cough, you release large and small particles. The larger particles travel a short way (six or so feet) and then settle to the ground, falling because of gravity. The smaller particles remain suspended in the air, traveling much farther and resisting the effect of gravity, Tierno says.
Both large and small particles can be released when someone coughs or sneezes, but also when people talk, sing and shout — you may remember the cluster of cases linked to a choir practice with one symptomatic person. The aerosolization of particles is related to the volume of vocalization, according to the authors of the case study.
Both types of particles are still respiratory droplets, Tierno says, so yes, technically, some respiratory droplets are truly airborne.
What’s the difference between aerosols and droplets?
Aerosols contain tiny droplets that can travel farther than large droplets.
Getty Images
The confusion continues. “The problem is that people use these terms interchangeably,” Tierno says, “when in reality they mean different things.”
You may have seen several terms floating around the internet, including droplet, aerosol and microdroplet. Microdroplets and aerosols are synonymous: These terms both refer to fine particles that can exist in the air for long periods of time and travel long distances. Droplets, on the other hand, are larger and do not travel as far.
There’s a longstanding (circa 1930s) standard in the medical and scientific communities that five microns serves as the “fence” between airborne particles and non-airborne particles. Anything larger than five microns is thought to settle to the ground within six feet — this belief informed the six-foot social distance barrier that’s now commonplace.
However, a letter from researchers published on Oct. 5 urges the scientific community to change this definition. A standard of 100 microns would be more appropriate, the researchers wrote, because in confined spaces, viruses in aerosols smaller than 100 microns can live for long periods of time.
Respiratory particles exist on a continuum, Allen says. “The reality is that [people] release particles of many different sizes, from less than five microns to way more. The medical community has long thought that a five-micron particle settles to the ground in less than six feet, but this is not always the case.”
Other factors, like ventilation, environment and velocity can affect how quickly a particle of any size settles, he says. Cigarette smoke might help you visualize this — if you stand 15 feet away from someone smoking a cigarette outdoors and the wind is still, you probably won’t notice the smoke. But with a breeze, the particles of cigarette smoke will quickly travel to you, even with that distance of 15 feet.
“The point for the public is this: There are a range of sizes [of particles], some of which can travel longer than six feet,” Allen says.
Has COVID-19 been airborne this whole time?
According to many scientists and doctors, the CDC has severely lagged in identifying the novel coronavirus as airborne. The same thing happened during the early months of the pandemic, when the CDC and WHO delayed labeling it a pandemic.
Many scientists and doctors began lobbying the CDC as early as February 2020 in an attempt to get the public health agency to classify SARS-CoV-2 as an airborne virus. In July 2020, nearly 250 scientists and doctors wrote an open letter to public health agencies urging them to address airborne transmission.
It’s unlikely anything fundamental — like the mode of transmission — has changed about the novel coronavirus since it began spreading in early 2020. It’s more likely that now, seven months in, the evidence is clear enough to definitely say COVID-19 can spread through airborne particles.
Fighting coronavirus: COVID-19 tests, vaccine research, masks, ventilators and more
See all photos
Why didn’t the CDC tell us the coronavirus was airborne?
Some say the CDC was trying to avoid adding to public fear or anxiety about the coronavirus, but this logic is faulty, Allen says. “This is risk communication 101,” he says. “You don’t hold back information. You have to be transparent about what’s happening to establish trust and allow people to act accordingly to protect themselves and others.”
Allen, who first wrote about airborne transmission of the coronavirus in February, says he doesn’t know what took the CDC so long to acknowledge airborne spread. “We [doctors] were excited a few weeks ago that they acknowledged it, and then they walked it back,” he says.
“The result is a confused public,” Allen says. “The science is what the science is,” and people can’t make informed decisions without knowing the truth. Allen says he supposes many more people would’ve taken basic precautions early in the pandemic had public health officials declared the virus airborne.
Others say the CDC’s lack of acknowledgement was of the presidency’s accord. “The CDC unfortunately is affected by the White House,” Tierno says. “Anything the CDC does can be politically infused. They may not have done this had they had no pressure on them.”
Does this mean the coronavirus is more infectious?
The coronavirus isn’t any more contagious than it already was, but this does reinforce the need for masks.
James Martin/CNET
No, the identification of airborne transmission doesn’t mean the novel coronavirus is more infectious than it already was.
“There’s a fundamental misunderstanding that all airborne viruses are highly infectious through airborne transmission,” Allen says. “Not all airborne viruses are like tuberculosis or measles,” both of which have high and rapid infection rates.
It does mean, however, that the standard of six feet isn’t always enough to prevent infection, especially in poorly ventilated areas.
It’s still not clear how many cases have occurred due to airborne transmission, and without a solid contact-tracing infrastructure, that’s something we may never know, says Allen.
How long does the coronavirus live in the air?
There’s no finite number of minutes or hours known yet. Estimates range from just a few hours up to 12 hours or more. Tulane University, for instance, reported that COVID-19 can remain in the air for up to 16 hours.
“‘Hours’ is typical, but remains largely undefined,” Tierno says, “which is an important consideration.”
Dr. Roshni Mathew, associate medical director of infection prevention and control at Stanford Children’s Health, says it’s important to remember that finding the virus’s RNA in air doesn’t automatically equate to transmission.
“Just having aerosols or finding virus particles does not equate to transmissibility, as there are other factors to consider,” she says, notably whether or not the virus is actually viable, meaning able to infect you. The WHO reports that in several studies that found virus particles in the air, the researchers did not find viable particles.
How far can the coronavirus travel in the air?
“The virus that causes COVID-19 is still under intense research,” Hamer says, “but it is understood that [larger] respiratory droplets from infected individuals can travel at least a few feet through the air to other persons within close contact.”
Aerosolized particles are lighter, so they are able to travel further through the air, Hamer continues, noting that some evidence has shown aerosols containing viruses can travel up to 18 feet. One study conducted in China suggests that aerosolized SARS-CoV-2 can spread up to four meters, or about 13 feet. Another report from April estimates the virus can spread up to 10 meters, or about 32 feet.
Again, environmental factors must be considered. Wind can carry particles, even larger ones, farther than six feet.
What this means for you
This means prevention practices are more important than ever.
Getty Images
Most importantly, everyone should be aware that airborne transmission of COVID-19 means six feet isn’t a magic number. The novel coronavirus can spread farther than that, and it’s important to keep that in mind, especially when indoors.
The current best practices for preventing the spread of COVID-19 are still our best protection, Hamer says. “The same personal protective measures should be adhered to, including wearing of face masks, good hand hygiene and practicing social distance measures,” he says, emphasizing that social distancing means at least six feet apart.
Knowing the novel coronavirus is airborne, people should pay more attention to the ventilation and air quality of their homes and other environments they frequent, Allen says.
“This reinforces the need for masks; it reinforces the fact that we shouldn’t be spending time indoors in crowded conditions or unventilated areas,” Allen says. “And it matters that the CDC said this.”
“It matters,” Allen emphasizes, “because before, it was just scientists saying it. It wasn’t official. Now it’s official, and going against this is going against [CDC] guidance.”
The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.
The Canadian government says it will donate up to 200,000 vaccine doses to fight the mpox outbreak in Congo and other African countries.
It says the donated doses of Imvamune will come from Canada’s existing supply and will not affect the country’s preparedness for mpox cases in this country.
Minister of Health Mark Holland says the donation “will help to protect those in the most affected regions of Africa and will help prevent further spread of the virus.”
Dr. Madhukar Pai, Canada research chair in epidemiology and global health, says although the donation is welcome, it is a very small portion of the estimated 10 million vaccine doses needed to control the outbreak.
Vaccine donations from wealthier countries have only recently started arriving in Africa, almost a month after the World Health Organization declared the mpox outbreak a public health emergency of international concern.
A few days after the declaration in August, Global Affairs Canada announced a contribution of $1 million for mpox surveillance, diagnostic tools, research and community awareness in Africa.
On Thursday, the Africa Centres for Disease Control and Prevention said mpox is still on the rise and that testing rates are “insufficient” across the continent.
Jason Kindrachuk, Canada research chair in emerging viruses at the University of Manitoba, said donating vaccines, in addition to supporting surveillance and diagnostic tests, is “massively important.”
But Kindrachuk, who has worked on the ground in Congo during the epidemic, also said that the international response to the mpox outbreak is “better late than never (but) better never late.”
“It would have been fantastic for us globally to not be in this position by having provided doses a much, much longer time prior than when we are,” he said, noting that the outbreak of clade I mpox in Congo started in early 2023.
Clade II mpox, endemic in regions of West Africa, came to the world’s attention even earlier — in 2022 — as that strain of virus spread to other countries, including Canada.
Two doses are recommended for mpox vaccination, so the donation may only benefit 100,000 people, Pai said.
Pai questioned whether Canada is contributing enough, as the federal government hasn’t said what percentage of its mpox vaccine stockpile it is donating.
“Small donations are simply not going to help end this crisis. We need to show greater solidarity and support,” he said in an email.
“That is the biggest lesson from the COVID-19 pandemic — our collective safety is tied with that of other nations.”
This report by The Canadian Press was first published Sept. 13, 2024.
Canadian Press health coverage receives support through a partnership with the Canadian Medical Association. CP is solely responsible for this content.
HALIFAX – The Nova Scotia government says it could be months before it reveals how many people are on the wait-list for a family doctor.
The head of the province’s health authority told reporters Wednesday that the government won’t release updated data until the 160,000 people who were on the wait-list in June are contacted to verify whether they still need primary care.
Karen Oldfield said Nova Scotia Health is working on validating the primary care wait-list data before posting new numbers, and that work may take a matter of months. The most recent public wait-list figures are from June 1, when 160,234 people, or about 16 per cent of the population, were on it.
“It’s going to take time to make 160,000 calls,” Oldfield said. “We are not talking weeks, we are talking months.”
The interim CEO and president of Nova Scotia Health said people on the list are being asked where they live, whether they still need a family doctor, and to give an update on their health.
A spokesperson with the province’s Health Department says the government and its health authority are “working hard” to turn the wait-list registry into a useful tool, adding that the data will be shared once it is validated.
Nova Scotia’s NDP are calling on Premier Tim Houston to immediately release statistics on how many people are looking for a family doctor. On Tuesday, the NDP introduced a bill that would require the health minister to make the number public every month.
“It is unacceptable for the list to be more than three months out of date,” NDP Leader Claudia Chender said Tuesday.
Chender said releasing this data regularly is vital so Nova Scotians can track the government’s progress on its main 2021 campaign promise: fixing health care.
The number of people in need of a family doctor has more than doubled between the 2021 summer election campaign and June 2024. Since September 2021 about 300 doctors have been added to the provincial health system, the Health Department said.
“We’ll know if Tim Houston is keeping his 2021 election promise to fix health care when Nova Scotians are attached to primary care,” Chender said.
This report by The Canadian Press was first published Sept. 11, 2024.
ST. JOHN’S, N.L. – Newfoundland and Labrador‘s chief medical officer is monitoring the rise of whooping cough infections across the province as cases of the highly contagious disease continue to grow across Canada.
Dr. Janice Fitzgerald says that so far this year, the province has recorded 230 confirmed cases of the vaccine-preventable respiratory tract infection, also known as pertussis.
Late last month, Quebec reported more than 11,000 cases during the same time period, while Ontario counted 470 cases, well above the five-year average of 98. In Quebec, the majority of patients are between the ages of 10 and 14.
Meanwhile, New Brunswick has declared a whooping cough outbreak across the province. A total of 141 cases were reported by last month, exceeding the five-year average of 34.
The disease can lead to severe complications among vulnerable populations including infants, who are at the highest risk of suffering from complications like pneumonia and seizures. Symptoms may start with a runny nose, mild fever and cough, then progress to severe coughing accompanied by a distinctive “whooping” sound during inhalation.
“The public, especially pregnant people and those in close contact with infants, are encouraged to be aware of symptoms related to pertussis and to ensure vaccinations are up to date,” Newfoundland and Labrador’s Health Department said in a statement.
Whooping cough can be treated with antibiotics, but vaccination is the most effective way to control the spread of the disease. As a result, the province has expanded immunization efforts this school year. While booster doses are already offered in Grade 9, the vaccine is now being offered to Grade 8 students as well.
Public health officials say whooping cough is a cyclical disease that increases every two to five or six years.
Meanwhile, New Brunswick’s acting chief medical officer of health expects the current case count to get worse before tapering off.
A rise in whooping cough cases has also been reported in the United States and elsewhere. The Pan American Health Organization issued an alert in July encouraging countries to ramp up their surveillance and vaccination coverage.
This report by The Canadian Press was first published Sept. 10, 2024.
