The Origin of the Ebola Virus

In 1976, Ebola (named after the Ebola River in Zaire) first emerged in Sudan and Zaire. The first outbreak of Ebola (Ebola-Sudan) infected over 284 people, with a mortality rate of 53%. A few months later, the second Ebola virus emerged from Yambuku, Zaire, Ebola-Zaire (EBOZ). EBOZ, with the highest mortality rate of any of the Ebola viruses (88%), infected 318 people. Despite the tremendous effort of experienced and dedicated researchers, Ebola's natural reservoir was never identified. The third strain of Ebola, Ebola Reston (EBOR), was first identified in 1989 when infected monkeys were imported into Reston, Virginia, from Mindanao in the Philippines. Fortunately, the few people who were infected with EBOR (seroconverted) never developed Ebola hemorrhagic fever (EHF). The last known strain of Ebola, Ebola Cote d'Ivoire (EBO-CI) was discovered in 1994 when a female ethologist performing a necropsy on a dead chimpanzee from the Tai Forest, Cote d'Ivoire, accidentally infected herself during the necropsy.

THE DEADLIEST EBOLA VIRUS

The deadliest Ebola outbreak in recorded history is happening right now. And now the Liberian government has confirmed that a senior doctor working to fight the disease, Samuel Brisbane, has died, the Associated Press reports. That makes him the first Liberian doctor to die of Ebola in the current outbreak.
In addition, an American doctor has been infected. Kent Brantly, a 33-year-old working for American aid organization Samaritan's Purse, has been treated and is in stable condition, according to USA Today.

This news comes just days after an announcement that the top Ebola doctor in Sierra Leone, Sheik Umar Khan, had been infected.
Brisbane's death is an unfortunate blow in a long battle that doesn't look like it's slowing down.
The current outbreak has killed 672 people and infected about 1,200
Liberia is one of several countries battling the current outbreak, which is unprecedented both in the number of cases and in its geographic scope. It's now hit four countries: Sierra Leone, Guinea, and Liberia have been joined by Nigeria, which this week saw its first case, after an infected Liberian man flew to the Nigerian city of Lagos, which is also Africa's largest city. There are also fears the disease has spread to the country of Togo, where that man's flight had a stopover.
And the virus — which starts off with flu-like symptoms and often ends with horrific hemorrhaging — had as of July 23 infected 1,201 people in Sierra Leone, Guinea, and Liberia, and killed an estimated 672 since this winter, according to the numbers from the World Health Organization.
Ebola is both rare and very deadly. Since the first outbreak in 1976, Ebola viruses have infected thousands of people and killed about one-third of them. Symptoms can come on very quickly and kill fast:

Why is Ebola back in the news?

Ebola tends to come and go over time.

The viruses are constantly circulating in animals, most likely bats. Every once in a while, the disease spills over into humans, often when someone handles or eats undercooked or raw meat from a diseased ape, monkey, or bat. An outbreak can then happen for several months. And then it becomes quiet again.

Ebola can completely disappear from humans for years at a time. For example, there were zero recorded cases of Ebola in 2005 or 2006.

Does Ebola really make people bleed from their eyes?

Yes. Bleeding from orifices is one of the more unusual and memorable symptoms of viral hemorrhagic fevers like Ebola. In later stages of the disease, some people bleed from the eyes, nose, ears, mouth, and rectum. They may also bleed from puncture sites if they've had an IV.
External bleeding can be one of the main symptoms that can help people realize they're dealing with a case of Ebola, since other signs — first fevers and headache, then vomiting and diarrhea — can be caused by any number of illnesses. Internal bleeding can happen, as well.
But it doesn't always happen. For example, this study of a 1995 outbreak in found external bleeding in 41 percent of cases. And bleeding didn't correlate with who survived and who didn't.
What actually kills people is shock from multiple organ failure, including problems with the liver, kidneys, and central nervous system.
Symptoms come on abruptly after an incubation period of 2 to 21 days. And people generally die between day 6 and 16 of the illness.

Why is Ebola so deadly?

One of the main things that seems to make Ebola viruses especially deadly is that they seem to be able to evade much of the human immune system. Among other problems, white blood cells from the immune system are often seen to die off in patients. And if the body can't fight fully back, the virus can just keep taking over.

Scientists are still figuring out exactly how this happens, and they have several promising leads. One is that the virus is making proteins that act as decoys, interfering with the body's ability to fight back.

How hard is it to catch Ebola?

Ebola is relatively hard to catch. Unlike measles or the flu, it's not spreadable over the air through casual contact.
In order to get Ebola, someone must touch the blood or bodily fluids (including sweat, urine, and semen) of a person or animal who's infected (alive or dead). People can also catch it through indirect contact with victims' fluids, such as via bedding or medical equipment.
People generally aren't infectious until they get sick.
This limited transmission ability is one of the main reasons why Ebola outbreaks can often be stopped within weeks or months. What it takes is public education and good health-care hygiene like patient isolation, sterilization procedures, and the use of gloves and masks.