How Ebola Works

Meet the Filovirus Family

Ebola is a beast of a virus, an evil villain disguised as a worm-like particle that invades your cells with no regard for life. And Ebola isn't just one evil villain; it's a whole family of five, with a not-too-distant cousin that sometimes visits, the Marburg virus (see sidebar). Beware any family that moves on to your block with the last name "Filovirus."

But unless you live in central or west Africa, you aren't that likely to come across the filoviruses. That's where four of these Ebola types originated. There's the Zaire and Sudan strains, which are the most deadly for humans, as well as the Bundibugyo and Tai Forest varieties, which have only been seen a few times. The fifth type, Reston, is the only non-African variety, having originated in the Philippines, and as far as we know, it's not deadly to humans.

Like all families, the filovirus family members look like each other. Same eyes, same red hair ... well, not really. We're talking about something here that's only about one-sixth as long as a human hair is wide. The worm-like shape of a filovirus is often described as "hooked," like a shepherd's crook. They all get their genetic material from RNA, instead of DNA the way we do. And their genetic information is not terribly complicated. While humans have 3 billion base pairs in their DNA, the molecules that make up the RNA of a filovirus only number about 19,000 [source: Smith].

Of course, the biggest likeness among the filoviruses is that they all kill their victims very similarly.

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