The Centers for Disease Control and Prevention confirmed Sunday that a nurse at a Dallas hospital who cared for Thomas Eric Duncan, who died from Ebola last week, was the first person to become infected with the virus on U. S. soil.
The nurse reportedly wore a gown, gloves, a mask and a face shield while caring for the Liberian national at Texas Health Presbyterian Hospital. Many, including CDC Director Tom Frieden, are questioning how the nurse became infected despite wearing the appropriate personal protective equipment, which should have shielded her from direct contact with Duncan and his bodily fluids.
Once again, the specter of airborne Ebola is being raised.
No virus that causes disease in humans has ever been known to mutate to change its mode of transmission. This means it is highly unlikely that Ebola has mutated to become airborne. It is, however, droplet-borne — and the distinction between the two is crucial.
Chickenpox, measles and tuberculosis are airborne diseases. Droplets of mucus and other secretions from the nose, mouth and respiratory tract transmit other diseases, including influenza and smallpox.
When someone coughs, sneezes or, in the case of Ebola, vomits, he releases a spray of secretions into the air. This makes the infection droplet-borne. Some hospital procedures, like placing a breathing tube down a patient’s air passage to help him breathe, may do the same thing.
Droplet-borne germs can travel in these secretions to infect someone a few feet away, often through the eyes, nose or mouth. This may not seem like an important difference, but it has a big impact on how easily a germ spreads. Airborne diseases are far more transmittable than droplet-borne ones.
Richard Preston‘s remarkable book, “The Hot Zone,” chronicled an Ebola Reston virus outbreak at a primate quarantine facility just outside Washington. The monkeys didn’t have direct contact with each other. CDC and military experts had to consider the possibility that Ebola Reston virus might be airborne. But feces thrown about the room, aerosols used in pressure washing the monkey cages or contaminated gloves used to handle the animals could also have transmitted the virus.