How Is Ebola Transmitted? WHO Offers Guidance

Brenda Goodman

October 06, 2014

Amid continued confusion over how Ebola spreads, the World Health Organization issued new guidance on Monday aimed at public education. 

First, the agency says, the virus is not airborne. Catching it through the air would depend on getting an infectious dose of the virus from a suspended cloud of tiny particles.

That’s how diseases like the flu and measles are spread.

Those viruses become airborne because specific cells that line the lungs and nose release a fine spray of viral particles into the air, says Elke Muhlberger, PhD. She’s a microbiologist at the Boston University School of Medicine who specializes in the study of Ebola.

People don’t even need to have symptoms to spread those diseases, she says. Ebola, on the other hand, is contagious only when someone has symptoms.

Scientists have been studying Ebola for decades, and they’ve never seen the disease passed through the air, according to the WHO. What’s more, it’s highly unlikely that the virus could change to become airborne.

The only way Ebola gets into the air is in large droplets of vomit or saliva. These droplets are heavy and wouldn’t be able to travel very far.

In theory, people might be able to catch it if someone coughed or sneezed directly onto them, but people who get Ebola generally don’t cough or sneeze.

What’s more, the WHO says it’s not aware of any studies that have ever shown the virus spreading this way.

Catching Ebola from someone else requires “close and direct” contact with infected body fluids, the WHO says. The most infectious body fluids are blood, stool, and vomit.

The virus has also been found in breast milk and urine -- and in semen for up to 70 days, though those fluids are considered to be less infectious.

Finally, the WHO says saliva and tears may also carry some risk, but it says more research is needed.

In studies of saliva, the virus was only found in people who were in advanced stages of the disease. The live Ebola virus has never been found in sweat, the WHO says.

The CDC says that in a single study, done under ideal conditions, the virus has been found to remain active on solid surfaces for up to 6 days.

In theory, then, a person might be able to touch a contaminated surface, rub their nose or eyes, and become infected.

But the WHO believes the risk of getting the disease this way is probably low. You can cut that risk even further by properly cleaning and disinfecting surfaces.

SOURCES:

News Release, World Health Organization.

Elke Muhlberger, PhD, microbiologist, Boston University School of Medicine, Boston.

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