Droplet spread versus airborne spread: #Ebola is droplet spread

Ebola virus disease (EVD) cannot be communicated in an airborne fashion like a cold or flu. Yet it is still very contagious if there is direct contact with an infected individual's bodily fluids (especially blood, urine, feces, vomit).

The CDC has a helpful infographic (Figure 1) on the important distinction between airborne spread versus droplet spread:

1. Airborne spread "happens when a germ floats through the air after a person talks, coughs, or sneezes. Germs may land in the eyes, mouth, or nose of another person."

2. Droplet spread "happens when germs traveling inside droplets that are coughed or sneezed from a sick person enter the eyes, nose, or mouth of another person. Droplets travel short distances, less than 3 feet (1 meter) from one person to another. A person might also get infected by touching a surface or object that has germs on it and then touching their mouth or nose."

A key takeaway is that droplets can travel only short distances (less than 1 meter).

The reason why is that a droplet is physically bigger than the aerosols (1 micron or less in diameter) that carry airborne pathogens. As a result a droplet cannot travel as far and is much less likely to be inhaled. This is why you cannot contract EVD from being in the same room (or same airplane) as an Ebola infected individual especially if the person is not showing symptoms.

The people most at risk are family members or medical personnel who have the potential of being in direct contact with a symptomatic person's bodily fluids. It should be noted that a sick Ebola patient is losing large quantities of fluid (blood, excrement, urine, and vomit; Ebola victims may need 10 to 20 liters of daily fluid replacement because of massive blood and fluid loss), and so droplets and fluid residue can be everywhere. Without protective gear, these droplets of bodily fluid would easily get on a persons's skin or in their nose and mouth.

Thus droplet spread does present considerable hazards in the presence of lots of droplets. Only symptomatic (i.e. sick) Ebola patients are capable of generating droplets in large quantities.

Figure 1. CDC infographic explaining the difference between droplet spread and airborne spread. Ebola is spread via droplets (courtesy of CDC).