Ebola is the nightmare virus. It kills ninety percent of people infected, and was for some time feared as the second coming of the plagues of the 1400s. Why is this one virus so much more deadly than other viruses?

Ask people to pick a virus that might, under the right circumstances, end the world, and they'll generally say "ebola." This is a virus that's known for its deadliness, and it earned its reputation. There are five different strains of ebola, and each is named after the zone in which it first turned up. Ebola's least deadly strain is Reston, which was first discovered in monkeys in a quarantine facility in Reston, Virginia. It was traced to the Philippines, where it seems to reside in both wild and domesticated pigs. This discovery caused a panic in the US, a bestselling book, and a blockbuster movie, but this version of the virus is completely asymptomatic in humans. It has never killed anyone.

Ebola's deadliest strain is Zaire. It was the first strain discovered in 1976, when it killed nearly 300 people. It's a hemorrhagic fever, which means it attacks the vascular system, wearing down blood vessel walls and preventing blood from clotting. All hemorrhagic fevers are dangerous, and none have any real course of treatment to attack the virus, as opposed to drugs meant to minimize complications and techniques prevent dehydration. A relative of ebola, Marburg fever, kills forty-to-eighty percent of those infected, but the Zaire strain of ebola has a ninety percent fatality rate. Of the hemorrhagic fevers, why does ebola stand out?


Researchers have found that people have died from ebola without ever having an immune response to the virus. The first lines of the defense of the immune system are dendritic cells. Dendritic cells are long, branched cells that line nearly every part of the body that has contact with the outside world. They cover the skin so completely that they were mistaken for nerves by early anatomists. They also crowd the mucosal linings of the lungs, nasal passages, and digestive system. When they come into contact with something that shouldn't be in the body, they grab it, break it apart, and take it to the immune system and display it - and get ripped apart themselves for their trouble. Then the body, properly alerted, starts working on a counterattack. Ebola, particularly the Zaire strain, has the ability to prevent the dendritic cells from manufacturing proteins that cause the immune system to destroy the dendritic cells when they're infected. The ebola virus doesn't set off an alarm, and can keep infecting the body at will.

Researchers have shown that mutating the virus in any of four areas destroys its stealth capabilities. Scientists have also figured out how ebola gets into cells, and have developed an antibody that can prevent infection. Perhaps it won't always be the terror it is now.


Top Image: CDC/Cynthia Goldsmith

Via Popular Science, The Rockefeller University, Mayo Clinic, Baylor College of Medicine.