After a few reports came out regarding the airborne transmission of the novel coronavirus, the World Health Organization has released new guidelines on Tuesday on the transmission of Covid-19 but refused to confirm that the virus spread through the air.
Few Covid-19 outbreaks have been reported in crowded indoor places, which suggest the possibility of aerosol transmission like in restaurants, fitness classes, or during choir practice, WHO acknowledged in its latest transmission guidance.
However, further research is urgently required to study such instances and investigate their significance for COVID-19 transmission, said WHO.
Previously, a group of aerobiologists who specialize in the spread of disease in the air had issued an open letter that urged WHO to update its guidance on COVID-19 to include aerosol transmission.
Based on the evidence available so far, WHO said the COVID-19 coronavirus spread through close contact with the infected people or with surfaces contaminated with the infected individual’s saliva, droplets, or respiratory secretions released while sneezing, speaking, singing, or coughing.
The new guidelines released by WHO warn people to avoid crowds and, in addition to social distancing, maintain good ventilation in buildings and wear masks when physical distancing is not possible.
Jose Jimenez, a chemist at the University of Colorado who signed the letter published on Monday in the journal Clinical Infectious Diseases, said it is becoming clear that the pandemic is driven by super-spreading events, and that the best explanation for many of those events is the aerosol transmission.
But there isn’t enough evidence yet on the airborne transmission of SARS-CoV-2, said Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases in a press briefing on Thursday. But he also added that its reasonable to assume the possibility. And that’s why they are asking people, especially those without symptoms to wear masks, to see if it can mitigate the spread of COVID-19.
According to the previous COVID-19 guidelines released by WHO, specific medical procedures were considered the only chances of airborne transmission of the SARS-CoV-2 before.
An aerosol expert at Virginia Tech, Linsey Marr, who contributed to the letter, encouraged the World Health Organization for acknowledging the possibility of airborne transmission.
But Linsey Marr also said that WHO is using an outdated definition of droplets and aerosols, and they are too focused on the size and distance droplets travel.
Not many diseases spread through tiny floating particles or aerosols. They include two highly contagious pathogens tuberculosis and measles that can remain in the air for hours and hence require extreme precautions to prevent exposure.
According to WHO, aerosols are particles that can float in the air for long, with a size under 5 microns. But much larger particles can also contribute to infection, said Jimenez and Marr.
They said the droplets and aerosols should be distinguished based on how infection occurs, not on size. If a person is infected by contact, they are droplets, and if infected by inhaling viruses, they are aerosols.
Breathing aerosols is a concern when the individuals are in close contact or in the same room, said Marr.
Editor’s Note; WHO release new guidelines for COVID-19, Calls for evidence on airborne transmission