nature | On 28 March 2020, two months after the WHO had declared COVID-19 a global health emergency, the agency broadcast a public-health message on Twitter and Facebook. “FACT: #COVID19 is NOT airborne,” it said, labelling claims to the contrary as misinformation. But evidence quickly established that the virus is transmitted by air, and researchers roundly criticized the agency.
The WHO updated its advice on SARS-CoV-2 transmission three months later, acknowledging the possibility that airborne transmission might occur in some community settings. Airborne transmission in “crowded and inadequately ventilated spaces over a prolonged period of time with infected persons cannot be ruled out”, the updated advice says.
Yuguo Li, a building environment engineer at the University of Hong Kong, says that he is disappointed it took the WHO and other health authorities so long. “We would have saved a lot of people” if airborne transmission was recognized earlier, he says.
A WHO spokesperson says the agency has mentioned the importance of ventilation since early in the pandemic.
Others say that the WHO’s position still doesn’t go far enough. “Airborne transmission is dominant,” says environmental epidemiologist Joseph Allen at Harvard University’s T. H. Chan School of Public Health in Boston, Massachusetts. That’s why building controls such as ventilation and air filtration make sense, he says.
The WHO and other health authorities have failed to clearly prioritise measures to improve indoor air quality to reduce the chance of catching COVID-19, says Jose-Luis Jimenez, an atmospheric chemist at the University of Colorado at Boulder. “They don’t emphasize how important it is,” he says. What the WHO needs to say is “fact, it goes through the air,” says Jimenez, “we breathe it in.”
A stark message from the WHO would ensure that national health authorities take notice, says Jimenez. Australia, the Netherlands and some other nations still do not acknowledge in their public statements that airborne transmission has a significant role in spreading the SARS-CoV-2 virus.
By the start of this year, concerns over ventilation had reached boiling point. Hundreds of health-care workers, scientists, engineers and occupational health-and-safety experts signed open letters calling on government officials in Canada, the United States, Australia, Colombia and the United Kingdom to address, among other things, poor indoor air quality. These concerted campaigns all urged local or national governments to take steps to reduce airborne transmission of SARS-CoV-2.
One of the problems is that governments and businesses are still spending millions of dollars on surface disinfection, says Jimenez, despite evidence that it is rare for SARS-CoV-2 to pass from one person to another through contaminated surfaces. By contrast, few countries have invested in measures to improve indoor air quality.
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