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FAQ: The Deadly Ebola Virus

By Rita Rubin
WebMD Health News

Editor's note: This story was updated on July 29, 2014.

April 4, 2014 -- Perhaps no virus strikes as much fear in people as Ebola, the cause of a deadly outbreak in West Africa.

The World Health Organization reports more than 1,200 cases of Ebola in the countries of Guinea, Liberia, and Sierra Leone as of July 23. More than 670 people have died.

Some of those cases are in health care workers. On July 28, the CDC said two Americans had been infected with Ebola, both in Liberia. One developed a fever but no other symptoms. The other was placed in isolation. The second person's family had been living with him in Liberia but returned to the United States before he became sick. Those relatives were placed on a 21-day fever watch, according to the CDC.

Ebola was first identified in 1976, when it appeared in outbreaks in Sudan and the Democratic Republic of the Congo. It is named for the Ebola River, which runs near the Congolese village where one of the first outbreaks happened.

WebMD asked Amesh Adalja, MD, about the virus and efforts to contain it. Adalja is an infectious disease physician at the University of Pittsburgh.

Q. How deadly is Ebola?

A. The Ebola strain in the current outbreak is the most lethal of the five known strains of the virus. It is called Ebola Zaire and usually kills up to 9 out of 10 infected people. But the high death rate might be due to a lack of modern medical care, Adalja says. “It’s hard to say exactly what the [death] rate would be in a modern hospital with all of its intensive care units.”

On July 28, the CDC said the Ebola death rate in the West African outbreak is actually about 6 in 10, rather than 9 in 10. That indicates early treatment efforts have been effective, says Stephan Monroe. He's the deputy director of the National Center for Emerging and Zoonotic Infectious Diseases at the CDC.

Q. What are the symptoms?

A. At first, the symptoms are like a bad case of the fluhigh fever, muscle aches, headache, sore throat, and weakness. They are followed quickly by vomiting, diarrhea, and internal and external bleeding, which can spread the virus. The kidneys and liver begin to fail.

Ebola Zaire kills people quickly, typically 7 to 14 days after symptoms appear, Adalja says.

A person can have the virus but not show any symptoms for as long as 3 weeks, he says. People who survive can still have the virus in their system for weeks afterward.

Q. How does the virus spread?

A. Ebola isn’t as contagious as more common viruses, such as colds, influenza, or measles, Adalja says. It spreads to people by close contact with skin and bodily fluids from infected animals, such as fruit bats and monkeys. Then it spreads from person to person the same way.

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