In a relentless sweep across Guinea, Liberia, and Sierra Leone, the largest outbreak of Ebola, a virus that causes dramatic internal bleeding and often a hasty death, has now claimed 467 lives, from 759 infections, since February this year, according to the World Health Organization (WHO).

With victims identified across more than 60 different locations, there's now a very real risk the outbreak will spread to even more countries, says Médecins Sans Frontičres (MSF), which calls the epidemic out of control.

WHO is now focusing on preparing for the disease's inevitable spread to neighboring countries, not a small ask in poor countries with poor health care systems. "We want other countries in West Africa to be ready—bordering countries, Ivory Coast, Mali, Senegal, Guinea Bissau—to prepare themselves in case people affected with the disease may be also traveling," WHO's Dr. Pierre Formenty told a recent briefing in Geneva.

In Ivory Coast, Guinea and Liberia's neighbor to the east, federal health officials have joined customs agents at the notoriously porous border in the hope of stopping the disease's spread; meanwhile, MSF has set up isolation centers nearby to contain infected persons if they do appear, says Anne Cugier, MSF's mission chief in that country. "We are all concerned about Ebola potentially spreading to Ivory Coast," she said.  

But Ebola is an elusive and very effective assassin, leaving scientists floundering to fit the pieces of the virology puzzle together. The science behind how and why Ebola spreads has yet to be fully nailed down—there's very little surveillance of the early stages of the disease deep in the African forests, where the disease may have been circulating in animals for a long time before "first contact" with humans. In this particular outbreak, it appears that the first diagnosed case was a doctor in the rural town of Gueckedou, whose infection then spread to health workers and family attending his funeral.

Researchers believe that butchering and eating infected "bushmeat"—a bat or gorilla, for example—usually serves as the first exposure to diseased animal blood.

Then, ritual funeral rites that involve rubbing down of dead bodies before interment bring relatives and others close to contaminated body fluids, after which Ebola's attack is swift and fatal in up to 90 percent of cases. Symptoms may appear anywhere from 2 to 21 days and include vomiting, diarrhea, and internal bleeding. Unlike the flu, Ebola is not airborne, so you can't get it from an infected person coughing or sneezing near you.

In Ivory Coast, the risk of Ebola transmission from bushmeat, which is a popular menu item at rural maquis—roadside outdoor grills—is considered high enough by federal health officials that it was recently banned altogether. But according to my colleague Tim McDonnell, who is in the country right now, there is no way to enforce the ban, and bushmeat is still being sold and eaten.

What is becoming clearer, however, is that human activity is playing a major role in the initial outbreaks of these zoonotic diseases—those that jump between animal and human—like Ebola. Humans are venturing farther and farther into forests, putting more and more pressure on local ecosystems through small-scale gold and diamond mining, deforestation, and conflict. In remote West Africa, where human populations meet the forests, people are increasingly coming into contact with animals, and that, combined with traditional hunting practices, is driving up the risk of a "spillover" occurring, where Ebola can leap across species.

For the complete article, please see Mother Jones.