CNN  — 

Imagine a noisy, crowded bar. Music is pounding, and people are clustered close together, talking loudly or even shouting to be heard. If it’s cold out, doors and windows are shut tight and the heat is on, or if it’s hot out, everything is shut and the air conditioner is recirculating the air.

This, in Donald Milton’s opinion, is the perfect situation for spreading coronavirus.

Not only could people pass the virus directly from one to another in the little droplets that we all spray to one degree or another when we talk, laugh or sing; but those little droplets also go up into the air where, Milton says, they can float around for at least some time.

Milton, a professor of environmental health at the University of Maryland who studies how viruses are transmitted, has helped lead a group of 239 scientists who wrote an open letter to appeal for better recognition of the potential airborne transmission of coronavirus.

It’s not a secret, but agencies seem to be afraid to talk about the airborne nature of the virus, Milton said.

“The airborne transmission word seems to be loaded,” Milton, one of two main authors of the letter, told CNN.

“The current guidance from numerous international and national bodies focuses on hand washing, maintaining social distancing, and droplet precautions,” Milton and colleagues wrote in the letter, published in the journal Clinical Infectious Diseases.

“Most public health organizations, including the World Health Organization, do not recognize airborne transmission except for aerosol-generating procedures performed in healthcare settings. Hand washing and social distancing are appropriate, but in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people,” they added.

‘They don’t want to talk about airborne transmission because that is going to make people afraid’

“I guess we are hoping that WHO will come around and be more willing to acknowledge the important roles of aerosols, whether they want to call it airborne transmission or not,” Milton said.

Milton studies the airborne transmission of viruses. The other main author, Lidia Morawska, is a professor of environmental engineering and an expert in aerosol science at the Queensland University of Technology in Brisbane, Australia. Milton said they and a group of other, similar experts have been discussing the potential airborne transmission of coronavirus since February.

Milton said the group wants to demystify the word so that health agencies will be less fearful about using it.

“They don’t want to talk about airborne transmission because that is going to make people afraid,” he said. There’s also an element of worry that if people think the virus is airborne, they’ll stop doing other things they need to do to prevent transmission, such as washing hands, staying apart and cleaning surfaces.

“The best vaccine against fear is knowledge and empowering people to take care of themselves,” Milton said. “I want them to understand to what extent washing their hands is important. Why wearing a mask is important is because it blocks the aerosols at their source, when it is easy to block them.” It’s harder to block aerosols once they are floating in the air, he said.