• WHO is considering updating its COVID-19 recommendations after its expert committees confirm the airborne spread of SARS-CoV-2 by aerosols
  • WHO currently holds only large droplets can spread SARS-CoV-2
  • Scientists fighting to get WHO to acknowledge aerosol transmission welcome its change of mind

The World Health Organization (WHO) seems to have come around to supporting the theory aerosols, or very small droplets, lingering in the air can spread the coronavirus that causes COVID-19.

On Tuesday, WHO acknowledged the possibility of COVID-19 being airborne and plans to update its advice on the transmission of SARS-CoV-2. WHO said a number of its expert committees are analyzing evidence on the transmission of SARS-CoV-2. It plans to release updated recommendations in a few days.

WHO admits airborne transmission is possible, especially in “crowded, closed, poorly ventilated settings, cannot be ruled out,” said Dr. Benedetta Allegranzi, a specialist in infectious diseases who leads WHO's committee on infection prevention and control, the New York Times reported.

This decision amounts to a sea change in WHO's current orthodoxy, which holds only larger respiratory droplets spewed outwards by an infected person sneezing, coughing or talking can spread SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), the virus that causes COVID-19. Up until now, WHO has dismissed a large body of evidence supporting SARS-CoV-2 particles floating indoors are infectious. It previously said research supporting this theory remains inconclusive.

But an open letter to WHO on Sunday signed by 239 scientists from 32 countries presented convincing evidence showing aerosols can infect people with SARS-CoV-2. These scientists say repeated COVID-19 outbreaks and infection clusters in many countries increasingly confirm SARS-CoV-2 aerosols linger in the air indoors and infect persons close by. The open letter is expected to be published in a peer-reviewed scientific journal this week.

Over the past few months, WHO's infection prevention committee has been weighing the evidence on all the ways in which SARS-CoV-2 spreads, including by tiny droplets or aerosols.

“We acknowledge that there is emerging evidence in this field, as in all other fields,” said Dr. Allegranzi.

“Therefore, we believe that 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.”

She said WHO will recommend “appropriate and optimal ventilation” of indoor environments, and physical distancing.

Signatories to the letter welcomed WHO’s announcement.

“We are very glad that WHO has finally acknowledged the accumulating evidence, and will add aerosol transmission indoors to the likely modes of transmission” for the coronavirus, said Prof. Jose-Luis Jimenez, who teaches chemistry at the University of Colorado Boulder.

“This will allow the world to better protect themselves and fight the pandemic.”

SARS-CoV-2 Scanning Electron Microscope Image
SARS-CoV-2 emerging from the surface of cells. National Institute of Allergy and Infectious Diseases