A group of health experts is warning that even tiny droplets of coronavirus from your mouth or nose can linger in the air and penetrate more deeply into your lungs.

An open letter published Monday by 239 scientists from around the world asks the World Health Organization (WHO) and other agencies to be more clear in explaining how the virus can transmit through the air.

The letter was published in the journal Clinical Infectious Diseases.

Donald Milton, a professor of environmental health at the University of Maryland, and Lidia Morawska, a professor of environmental engineering and an expert in aerosol science at Queensland University of Technology in Brisbane, Australia, were lead authors on the letter.

“The airborne transmission word seems to be loaded,” Milton told CNN.

The group wants to demystify the word so that health agencies will be less fearful about using it. Its members believe that the current guidance that focuses on hand washing, social distancing and droplet precautions in healthcare settings is not enough.

“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 wrote.

“They don’t want to talk about airborne transmission because that is going to make people afraid,” Milton told CNN. “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.”

The group gives practical advice to prevent airborne spread in its letter, per CNN:

• Provide sufficient and effective ventilation (supply clean outdoor air, minimize recirculating air) particularly in public buildings, workplace environments, schools, hospitals and nursing homes.

• Supplement general ventilation with airborne infection controls such as local exhaust, high efficiency air filtration, and germicidal ultraviolet lights. (These would be placed high up in the ceiling to avoid damage to people’s eyes and skin)

• Avoid overcrowding, particularly in public transport and public buildings.

In early April, a group of 36 experts on air quality and aerosols urged the WHO to consider the growing evidence on airborne transmission of the coronavirus, according to The New York Times. The WHO held a call with Morawska on airborne transmission but ultimately decided not to change the group’s guidelines.

Many experts told The New York Times that the WHO should embrace what some called a “precautionary principle” and others called “needs and values” — the idea that even without definitive evidence, the agency should assume the worst of the virus, apply common sense and recommend the best protection possible.