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An open letter signed by 239 researchers from 32 countries and sent to public health agencies, including the World Health Organization, on Monday says there is significant evidence to support thiscan remain in the air and spread from person to person in tiny particles in the air. The letter, published in Clinical Infectious Diseases on Monday, advocates "using preventive measures to mitigate this airborne pathway" and suggests re-examining the role of different pathways in the spread of disease.
The existence of the open letter was first reported on Saturday by the New York Times and the Los Angeles Times and described the WHO as an organization that "does not keep up with science" on this issue. On Thursday, WHO responded by updating its scientific report on the spread of the coronavirus.
It is pointed out that science has not yet decided whether SARS-CoV-2, the coronavirus that causes COVID-19, will effectively spread and cause airborne diseases. And it doesn't seem to be a yes or no equation. Like many aspects of the pandemic, it is a mystery that remains unsolved.
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"It is possible and even likely that SARS-CoV-2 will sometimes be airborne," said Babak Javid, an infectious disease doctor at Tsinghua University Medical School, in a statement. "It is not at all clear how common this is."
WHO's official guidance on this matter is that the virus moves from person to person through "small droplets" that are expelled when a person with COVID-19 coughs, sneezes, or speaks. These droplets are too heavy to travel long distances and quickly sink to the ground. The virus is also specified. That is why hand washing and social distancing are important to curb the spread.
However, the signatories to the open letter argue that SARS-CoV-2 is in the air, and this could play a role in the transmission. They believe that when a person releases COVID-19 viruses, the particles remain in the air and can travel long distances in air currents, especially in poorly ventilated areas. "It goes without saying that the transmission of SARS-CoV2 in the air is not yet widely accepted. However, in our collective assessment, there is more than enough evidence that the precautionary principle should apply," they write.
To reduce the risk of airborne transmission, they propose two important measures: better ventilation in public buildings and reduction of overcrowding. It also calls on WHO to identify this potential transmission route and to communicate the associated risks more effectively.
"We are concerned that the lack of recognition of the risk of COVID-19 transmission in the air and the lack of clear recommendations on control measures against the virus in the air will have significant consequences," the researchers write. WHO has been reluctant to provide additional advice highlighting the risks based on the lack of evidence.
Some scientists raised concerns about the letter, suggesting concerns about airborne transmission may be exaggerated.
"I'm a bit shocked that this happened," said Isaac Bogoch, an infectious disease researcher at the University of Toronto. "There is no new data, just a signed letter that makes the headlines."
Over the air
The debate focuses on the interpretation of the modes of transmission, and this confusion extends to the public's perception of how the disease spreads.
"One problem here is the potential conflict between the technical term air transmission and the public's perception of that term," said Jose Vazquez-Boland, infectious diseases chair at the University of Edinburgh.
The academic Kerfuffle essentially "droplets" – the heavy particles that fall to the ground within six feet – against "aerosols" – light virus particles floating in the air. The main difference is the size of the particles.
"The size of (a) droplets will be really important because they all have mass or weight," said Bruce Thompson, respiratory expert at Swinburne University in Australia. The larger breath droplets of something like a sneeze don't stay in the air for long; They are in the air, but fall quickly to the ground due to gravity. Aerosols are different.
"If it's an aerosol, it may be floating in the air more," says Thompson.
These technical differences can make it difficult for the public to understand what it means when a virus is "in the air".
"It can be difficult for the public to distinguish between different situations and technical definitions," said Vazquez-Boland.
You might immediately think that jogging or spending time outdoors could lead to infection if COVID-19 particles get into your lungs. However, it is more likely that the route will take place in the air in densely packed interiors with poor ventilation. Whether you can be infected with SARS-CoV-2 is likely context-specific, and many factors play a role. Part of this nuance is lost in academic back and forth and leads to public confusion about the spread of the disease.
"There is a wrong dichotomy between droplet and air transfer," said Bogoch. "It is more of a spectrum than silos.
"COVID-19 falls closer to the droplet end of the spectrum," said Bogoch.
Even if the risk is underestimated or underestimated by the WHO, it may not have a dramatic impact on fighting spread. The organization recommends avoiding crowded places to protect yourself from COVID-19. It also recommends people who feel sick to stay at home or wear a mask when leaving the house. This is another factor that limits the risk of airborne transmission.
Regardless of whether the coronavirus is in the air, the guidelines remain largely the same for the time being. Avoid crowded interiors or try to spend less time there when you need to be inside. The virus can accumulate in poorly ventilated rooms and increase the risk of infection.
You should continue to maintain social distance measures. When you're on the go. Wash your hands And keep listening to advice from local health authorities, with the caveat that information may and will change as a result of new knowledge.
During a press conference on Tuesday, journalists interviewed WHO about the New York Times report and open letter to give the organization the opportunity to speak publicly on the subject.
"We recognize that there is new evidence in this area," said Benedetta Allegranzi, a WHO technical leader in infection prevention and control. "We believe that we need to be open to this evidence and understand its impact on the transmission path."
"As we said, we welcome the interaction of scientists around the world," added Maria Van Kerkhove, technical director of the COVID-19 pandemic. "We are also investigating the role of air transfer in other environments where you are poorly ventilated," she noted. Van Kerkhove noted that WHO had been working on a "letter" for transmission for several weeks. The organization released the letter on Thursday, July 9th, which updates the March 29 "Modes of Transmission" statement.
WHO is now recognizing the emerging evidence of airborne transmission contained in the open letter, but the organization's new outline states that COVID-19 patients "primarily" infect others through droplets and close contact. The WHO has not "reversed" its guidelines, as some claim, but supplements them based on new evidence (and open letter), while recognizing that evidence of airborne transmission and SARS transmission remains low -CoV-2 through This type of aerosol route has not been detected. "
The importance of this route for the diffusion of COVID-19 is still under debate, and the updated WHO briefing states: "High quality research is urgently needed to clarify the relative importance of different transmission routes."
Updated July 7th: WHO briefing comments added.
Updated July 9: Adds a short scientific publication and WHO comments and updates the heading.