How Contagious Is Ebola & How Does it Spread?

This article is an excerpt from the Shortform summary of "The Hot Zone" by Richard Preston. Shortform has the world's best summaries of books you should be reading.

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How contagious is Ebola? Does Ebola spread easily from person to person?

When asking “how contagious is Ebola” it’s important to consider each of the four different strains of the virus, and how they spread. Ebola is spread through bodily fluids, with the exception of Ebola Reston, which may be airborne. However, Ebola Reston does not seem to infect humans the same way as other Ebola viruses.

So, how contagious is Ebola? Read to find out.

How Contagious is Ebola?

The Ebola virus targets its host’s immune system, preventing the host’s body from fighting off the disease. But viruses need a living host to survive, so when a victim dies, the virus must jump hosts. Ebola is transmitted through exposure to the blood or bodily fluids of an infected victim or corpse.

With the exception of Ebola Reston, filoviruses don’t appear to discriminate between people and animals, and they can jump easily from one to the other. 

Scientists still don’t know what the filoviruses’ hosts are—whether insects or animals—but the viruses can be transmitted to primates or duikers, a type of antelope. Nor do scientists know where the hosts live, but most cases originated in the region around Mount Elgon, on the border of Kenya and Uganda, not far from Sudan. Specifically, a few cases trace back to Kitum Cave, on the eastern slope of Mount Elgon.

(Shortform note: Scientists still don’t know the hosts of filoviruses, but evidence points to fruit- and insect-eating bats as major carriers—though that doesn’t rule out the possibility that an insect or rat is the original host and simply infected the bats through a bite. Scientists also suspect there could be multiple hosts.)

So how contagious is Ebola? Let’s find out.

How Contagious is Ebola? Examples of the Disease’s Spread

How contagious is Ebola? Scientists know that the disease spreads through bodily fluids, but how quickly the disease spreads can vary. Here are some examples from The Hot Zone.

Spreading at Hospitals

The virus appeared at the rural Yambuku Mission Hospital, which was run by Belgian nuns. No one knows who the first human was to contract Ebola Zaire, or from what—whether animal meat, insect blood, a spider bite, or something else. The hospital’s practice of reusing dirty needles made it impossible to know which patient first brought the virus into the hospital.

Just a drop of infected blood is enough to transmit Ebola, so the virus quickly spread among the hospital’s nurses, injection patients, and their families, hitting 55 surrounding villages at once.

The virus is extremely virulent and highly infective, and it can live in corpses’ eyeballs for months after death. 


The nurses wheeled Monet—barely alive—into the intensive care unit, where a young doctor named Shem Musoke inspected him. 

Musoke had no idea what kind of illness this was, but his first priority was to help Monet breathe, which was becoming increasingly difficult as he hemorrhaged and his airways filled with blood and mucus. Without wearing gloves, Musoke put his finger in Monet’s mouth to clear the blood and mucus so he could insert the laryngoscope. 

As Musoke leaned close to Monet’s face, peering down his throat, Monet spewed black vomit all over Musoke, the gurney, and the floor around them. Bits of vomit landed in Musoke’s eyes and mouth. 

An Airborne Contagion?

How contagious is Ebola? Can Ebola be airborne? The newest strain of Ebola, Ebola Reston, shows evidence of being airborne. USAMRIID researchers determined that this virus was a new form of Ebola. They named it Reston. 

This virus was so similar to Ebola Zaire that it was hard to distinguish them in microscopic images. But two things were significantly different about Ebola Reston.

First, Ebola Reston appeared to be airborne. While the virus spread through the monkey house, it infected monkeys in different rooms that never interacted. Additionally, two of the Reston employees who tested positive hadn’t been exposed through any cuts or blood contact, so they must have contracted the virus through the air. 

Second, unlike the other filoviruses, Ebola Reston didn’t appear to affect people. 

Still, researchers remained cautious. Considering how quickly the virus appeared to adapt, they couldn’t eliminate the possibility that one small mutation could make Ebola Reston lethal to humans—and its airborne transmission would make the threat even deadlier. 

How Contagious Is Ebola & How Does it Spread?

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Like what you just read? Read the rest of the world's best summary of Richard Preston's "The Hot Zone" at Shortform .

Here's what you'll find in our full The Hot Zone summary :

  • The many different strains of Ebola, including the deadliest kind with a kill rate of 90%
  • How scientists unraveled the mystery of a new strain of Ebola
  • How Ebola could become airborne, becoming one of the deadliest viruses known

Carrie Cabral

Carrie has been reading and writing for as long as she can remember, and has always been open to reading anything put in front of her. She wrote her first short story at the age of six, about a lost dog who meets animal friends on his journey home. Surprisingly, it was never picked up by any major publishers, but did spark her passion for books. Carrie worked in book publishing for several years before getting an MFA in Creative Writing. She especially loves literary fiction, historical fiction, and social, cultural, and historical nonfiction that gets into the weeds of daily life.

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