This archive report was first published on 10 July 2020.
On July 10, 2020, the World Health Organization (WHO) faced mounting pressure to reconsider its stance on Covid-19 transmission after 239 scientists signed an open letter urging it to recognize the airborne transmission of the virus.
The letter, published in the Journal of Clinical Infectious Diseases, argued that Covid-19 can be transmitted through breathing out, talking, and coughing, contradicting the WHO's assertion that aerosolized transmission is limited to hospital settings.
According to the WHO, aerosolized transmission is currently recognized in specific medical procedures such as endotracheal intubation, bronchoscopy, and non-invasive positive-pressure ventilation. However, the scientists argue that the virus can also be transmitted through the air in other settings.
"There is a significant potential for inhalation exposure to viruses in microscopic respiratory droplets at short to medium distances," the scientists wrote in the letter.
They cited studies that demonstrated the release of viruses in micro-droplets during exhalation, talking, and coughing, which can remain aloft in the air and pose a risk of exposure at distances beyond one to two meters from an infected person.
Retrospective studies conducted after the Sars-CoV-1 epidemic showed that airborne transmission was the most likely mechanism explaining the spatial pattern of infections. The scientists therefore undertook a similar study on Sars-CoV-2 and established the same pattern.
They also cited a Chinese restaurant where people got infected despite having no direct or indirect contact between them, and a study published in the Journal of Emerging Infectious Diseases that suggested droplet diffusion prompted by air-conditioned ventilation was the most probable route of transmission.
