Airborne spread of Covid-19 a real risk and cannot be ruled out, WHO to issue scientific brief after review
The World Health Organization (WHO) has acknowledged "emerging evidence" regarding the possibility of the airborne spread of Covid-19 and plans to issue a scientific brief in the coming days on different modes of transmission. The move comes after over 200 scientists called for greater acknowledgment of the role of airborne transmission of Covid-19 and the subsequent need for countries to implement preventive measures against this risk.
The WHO said that it is reviewing new evidence on whether the coronavirus can spread through particles in the air. "We acknowledge that there is emerging evidence in this field, as in all other fields, regarding the Covid-19 virus and pandemic. Therefore, we believe we have to be open to this evidence and understand its implications regarding the modes of transmission and also regarding the precautions that need to be taken," said Professor Benedetta Allegranzi, technical lead for infection prevention and control at WHO, during a briefing on Tuesday, July 7.
The expert said that the airborne transmission of Covid-19 cannot be ruled out in crowded or closed settings. "The possibility of airborne transmission in public settings, especially in very specific conditions, crowded, closed, poorly ventilated settings that have been described cannot be ruled out. However, the evidence needs to be gathered and interpreted, and we continue to support this," said Allegranzi.
Dr Maria Van Kerkhove, the WHO’s technical lead on Covid-19, said: "We have been engaged with this group since April when they first wrote to us on April 1. We welcome the interaction from scientists all over the world. We have been talking about the possibility of airborne transmission and aerosol transmission as one of the modes of transmission of Covid-19 as well as droplets. We are producing a scientific brief on summarizing where we are. We have been working on this for several weeks now. We have engaged with a large number of groups to try to consolidate the growing knowledge around transmission. We will be issuing our brief in the coming days and that will outline everything that we have in this area."
According to WHO’s existing guidance, the new coronavirus is transmitted primarily between people through respiratory droplets and contact routes. The WHO says airborne transmission may be possible in specific circumstances and settings in which medical procedures like intubation or support treatments that generate aerosols are performed.
In their open letter to WHO, published in Clinical Infectious Diseases, scientists appealed to the medical community and to the relevant national and international bodies to recognize the potential for airborne spread of Covid-19. "There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (microdroplets) at short to medium distances (up to several meters, or room-scale), and we are advocating for the use of preventive measures to mitigate this route of airborne transmission. Studies by the signatories and other scientists have demonstrated beyond any reasonable doubt that viruses are released during exhalation, talking, and coughing in microdroplets small enough to remain aloft in the air and pose a risk of exposure at distances beyond 1 to 2 meters from an infected individual," said the report.
Experts said that while it is understood that there is not yet universal acceptance of airborne transmission of SARS-CoV-2, the virus that causes Covid-19, but in their "collective assessment", there is more than enough supporting evidence so that the "precautionary principle should apply". "To control the pandemic, pending the availability of a vaccine, all routes of transmission must be interrupted. We are concerned that the lack of recognition of the risk of airborne transmission of Covid-19 and the lack of clear recommendations on the control measures against the airborne virus will have significant consequences: people may think that they are fully protected by adhering to the current recommendations. But in fact, additional airborne interventions are needed for further reduction of infection risk," they explained.
The scientists warned that the matter is of “heightened significance” now when countries are reopening following lockdowns. They have recommended measures to mitigate airborne transmission risk, which includes providing sufficient and effective ventilation, particularly in public buildings, workplace environments, schools, hospitals, and aged care homes, supplementing general ventilation with airborne infection controls such as local exhaust, high-efficiency air filtration and germicidal ultraviolet lights, and avoiding overcrowding, particularly in public transport and public buildings.
"We hope that our statement will raise awareness that airborne transmission of Covid-19 is a real risk and that control measures must be added to the other precautions taken, to reduce the severity of the pandemic and save lives," they emphasized. Dr Soumya Swaminathan, the WHO's chief scientist, said that the body of evidence continues to grow and "we adapt". "We take this very seriously. We are of course focused on public health guidance. So any guidance that we put out has implications for billions of people around the world. So it has to be carefully considered before it is done. We want to be as fast as possible and adaptive and responding to the new evidence. And at the same time, we have to consider the weight of the evidence," she said.