When the physicians found the nine-year-old boy he was scared and barely had a pulse. He had been locked in a house with his mother for four days by community members in a corner of southwest Guinea, the hotbed of Africa’s current Ebola crisis.

The boy’s neighbors were frightened of contracting the virus that causes the highly lethal illness (which kills between 50 and 90 percent of its victims) and did not want to risk coming into contact with either of them.

By the time that Doctors Without Borders came upon their village, however, it was too late—the mother died in the back of a pickup truck on the way over to the temporary Ebola clinic. The little boy trembled nearby, surrounded by workers wearing protective body suits, high rubber boots and masks fogged up with perspiration. When he got to the treatment center and received a small bag of cookies he managed a wan smile. Within the day he was dead. “He died by himself in an isolation treatment center,” says William Fischer, a pulmonary and critical care doctor who was working at the center that day in June, sent there by the World Health Organization (WHO) to fight the Ebola outbreak. “It definitely will take some years off my life.”

Past Ebola cases have cropped up in Zaire (now the Democratic Republic of the Congo) and Sudan since the first two outbreaks were recognized there in 1976. Recently, the disease has been found primarily in the DRC and Uganda. Until this year most cases occurred in remote areas abutting the rainforest where the unfortunates who contracted the disease were isolated and unable to travel far—thus limiting its spread.

This outbreak, which was first reported to the WHO in March, is much, much different. It’s occurring at the contiguous corners of three countries—Sierra Leone, Guinea and Liberia—that have very porous borders and where it has never previously been seen. It has the unique distinction of becoming the largest Ebola outbreak ever recorded, with more than 600 deaths and 1,200 infections to date. The strain that is causing it, investigators say, is genetically dissimilar to previous strains.

“It’s almost impossible to project the spread of the disease,” in the weeks and months ahead, says Anthony Fauci, executive director of the National Institute for Allergy and Infectious Diseases (NIAID). “There needs to be a much more concerted dramatic effort to stop it, and I don’t know where that’s going to come from.” Governments must restrict movement, get people into hospitals with proper hygiene practices and set up field hospitals where necessary, he says.

Ebola can look like flu at first, causing fever along with head and muscle aches. In latter stages it can progress into diarrhea, vomiting, rash and bleeding, ultimately leading to organ failure.

And, it’s only a plane ride away. “This is the first time Ebola has reached a city with an international airport and crossed international boundaries," Fischer says. He notes that last week Nigeria reported its first case of Ebola when an infected Liberian governmental official flew to Lagos, Nigeria’s (and Africa’s) most populous city. "I think this is a great example of how infectious disease and mobility can lead to devastation”

Over the weekend Liberia announced that it is closing some of its borders as part of its effort to control the disease outbreak. Yet even that might not be able to keep the flow of humans from crossing into and out of the country each day. (Officials at the U.S. Centers for Disease Control and Prevention say it is unlikely the virus will spread to the U.S. Nevertheless, they have sent out health alerts to U.S. providers about Ebola symptoms to watch for and instructed clinicians how to test for Ebola and take precautionary steps including isolating symptomatic patients).

The disease has been termed “totally out of control,” but as Fischer says, “I don’t know what an Ebola outbreak would look like that is under control.” Perhaps in a country with more resources and infrastructure, exposed individuals would be more carefully tracked, making it seem like the disease is more controlled. Alas, in west Africa, there is not much of a communication infrastructure to ensure proper disease prevention precautions are implemented.

The virus has an incubation period of a few days to three weeks. Unlike most pathogens, which cannot survive long on a corpse, however, Ebola does remain infectious after a person dies—for how long remains unknown. WHO notes that men who have survived the disease can still transmit the virus through their semen for up to seven weeks after recovery, providing a glimpse into the longevity of this potent pathogen.

In communities with a deep distrust of health care workers, families sometimes fear that leaving a sick patient at hospital may kill him, so instead they will take an Ebola-infected patient home. Then if he dies, and the family ritually washes and cleanses the body, they will unwittingly act as a handmaiden for the virus. Although the infectious disease is not transmitted just by breathing in the same space as an infected patient, people in close contact with the blood, diarrhea, vomit or saliva of a patient can contract the virus.

Right now the only treatments for Ebola are rehydration and painkillers.

Experts are still unclear about where Ebola comes from. There are documented cases of contracting the virus after someone is exposed to a fruit bat, bush meat or encountering an infected porcupine, but it’s undeniable that once the chain of human-to-human transmission gets going, it is deadly.

The outbreak can only be declared over after two successive incubation periods, or six weeks, have passed without incident. Yet when we could see such a period remains hard to pin down. “You can get lulled into thinking the epidemic is under control because the numbers will go down and then it’ll turn out that you missed [one infected person] and now it’s spreading to other people,” Fischer says. “I don’t think we are anywhere near the end” The NIAID's Fauci agrees. “I think it will go on for awhile,” he says.

The only macabre silver lining: the outbreak may provide a needed push forward for the development of a vaccine for Ebola. “We have a candidate, we put it in monkeys and it looks good, but the incentive on the part of the pharmaceutical companies to develop a vaccine that treats little outbreaks every 30 or 40 years—well, that’s not much incentive," Fauci says. “This will make people realize that this can get out of hand.”