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Droplet, Aerosol, Airborne, what’s the difference? And do I still have to wear a mask?

by Alexandra Wickson, MPH and Amy Sharma, PhD

You might have heard a lot of new terms recently used to talk about COVID-19. Aerosol, droplet, and airborne are a few that are commonly used to discuss how COVID-19 spreads.

Below we explain these terms. But if you are in a hurry, TLDR: “Regardless of droplet vs aerosol – a mask is still the best defense. Wear a Mask!”

Droplets and aerosols are respiratory particles created when you cough, sneeze, or talk. The World Health Organization (WHO) defines respiratory droplets and aerosols by size: droplets are >5-10 micrometers (μm) in diameter whereas aerosols are <5μm. Aerosols can also refer to tiny respiratory particles created during medical procedures such as intubation, which are referred to as “aerosol-generating procedures.”

Airborne transmission is defined as spread through aerosols that are still infectious “when suspended in air over long distances and time” (WHO). Examples of diseases that are airborne include pulmonary (lung) tuberculosis and measles. For example, measles can “live for up to two hours in an airspace where the infected person coughed or sneezed” (CDC).

We know that COVID-19 is spread through droplets and aerosol-generating procedures in medical facilities (WHO). But whether COVID-19 is spread through aerosols between people or is airborne is not fully understood yet (WHO).

This illustration shows how far a droplet vs. an aerosol can go. 1m is approximately 3 ft. Standing 6 ft away is double the typical range of large droplets – which is where the “stand 6 feet apart” directive comes from. Illustration Credit.

WEAR A MASK! While this debate is important for science and the study of the disease, it does not change the precautions we are taking. 6 ft apart prevents the largest (and greatest chance of infection) droplets from reaching you. Wearing a mask reduces the number of particles regardless of droplet or aerosol.

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