Confusion reigns as CDC takes down guidance that confirmed aerosol transmission

A draft of the proposed changes to its recommendations, which was later withdrawn pending finalisation, the CDC confirmed that airborne particles can spread even by breathing, remain suspended in air and be inhaled and spread beyond six feet in certain enclosed settings.

The Centers for Disease Control and Prevention (CDC) is revising its guidelines to acknowledge the spread of the novel coronavirus through aerosols, and to point to inhalation of particles as one of the ways the virus spreads.

A draft of the proposed changes to its recommendations posted on September 18, which was later withdrawn on September 21 pending finalisation , confirmed that airborne particles can spread even by breathing, remain suspended in air and be inhaled and spread beyond six feet in certain enclosed settings.

The much-delayed acknowledgement comes after a body of evidence provided sufficient indication of aerosol (less than 5 microns) transmission of the virus especially in closed settings with poor ventilation and after prolonged contact with an infected person. In the first week of February, Chinese researchers from the Wuhan Institute of Virology in a paper published in Nature first proposed that the virus could spread through airborne transmission. That paper is particularly important as it also identified and characterised the novel coronavirus and confirmed the receptor to which the virus binds.

The delay by CDC in acknowledging aerosol transmission becomes even more inexplicable as the World Health Organization had on July 9 acknowledged that novel coronavirus can be airborne in closed settings after more than 200 scientists published in a journal an open letter appealing to the medical community and national and international bodies to “recognize the potential for airborne spread of COVID-19”.

Beginning with the cruise ship Diamond Princess, large outbreaks have been documented in churches in South Korea and Singapore, prisons, old-age homes, Zumba classes in South Korea, ski resorts in Austria and choir practice in a church in Mount Vernon, Washington. These outbreaks have provided strong evidence for aerosol transmission in certain closed settings early during the pandemic.

It is therefore bewildering that both the WHO and CDC refused to adopt the precautionary principle and caution people of potential aerosol spread of the virus in certain settings even while collecting data to confirm or refute that possibility.

Surprisingly, even in the absence of any guidelines from the global bodies, many countries had on their own denied permission for certain enclosed settings such as restaurants, bars, theatres, gyms, and religious places to operate thus averting innumerable outbreaks and cases.

With aerosol transmission now being confirmed and its spread to distances beyond six feet also known, the only way to prevent infection till such time and probably even when vaccines become available is through universal masking. Timely cautioning by global bodies of aerosol transmission possibility might have encouraged universal mask wearing early on, thus preventing thousands of cases.

Universal masking can avert infections, and if infected, the amount of viral load one is exposed will be less thus leading to only asymptomatic infections or mild disease. Unlike Diamond Princess, universal masking in another ship led to 81% of infections being asymptomatic. Similar results have been seen in other cases where universal masking was practised.

With aerosol transmission now being established as the most likely way by which the virus spreads in certain settings, the best way to avoid getting infected is by staying clear of crowded, closed settings that have poor ventilation.

Published in The Hindu on September 22, 2020