The largest outbreak of Ebola in history is suspected of killing 670 people in West Africa and there are fears that it could spread. Here’s what you need to know.

What is Ebola?

“Ebola virus disease (EVD), formerly known as Ebola hemorrhagic fever, is a severe, often fatal illness in humans,” the World Health Organization (WHO) says.

Where is the outbreak happening?

The outbreak of the disease is in Sierra Leone, Liberia, Guinea and Nigeria.

As of July 23, the WHO had confirmed more than 800 Ebola cases in the region, but suspects there have been many unreported infections and there may be more like 1,200 cases. Sierra Leone has been hardest hit with approximately 525 cases.

How many people have died?

The WHO says as of July 23, there have been 456 confirmed Ebola deaths, and another 216 suspected deaths, bringing the number possibly to more than 670.

Guinea has the most suspected deaths. The epidemic has been in that country longer. It is believed the epidemic began in the nation’s capital of Conakry.

While international leaders have mobilized to fight the epidemic, it can be a difficult one to stop. It is so highly infectious that it typically kills 90 per cent of those who catch it. The death rate in this particular outbreak has dropped to roughly 60 per cent since it has been treated early in many instances. There is, however, no Ebola vaccination.

What are the symptoms?

Symptoms include fever, sore throat, chills, muscle aches, nausea, vomiting, diarrhea, impaired kidney and liver function, and internal and external bleeding.

It takes two to 21 days from the time a person is infected to when he or she shows symptoms.

Ebola is not contagious until symptoms appear, though that doesn’t mean a person cannot travel in the incubation period.

Could Ebola spread to Canada?

There has never been a confirmed case of Ebola spreading to a developed country, said Kamiliny Kalahne, an epidemiologist with Doctors Without Borders in the U.S.

“This is because people generally transmit the infection when they are very sick, have a high fever and a lot of symptoms — and in these situations, they don’t travel.

“And even if they do get sick once they travel to a developed country, they will be in a good hospital with good infection control, so they are very unlikely to infect others,” she said.

What is being done?

West African airline Asky has suspended flights to Liberia and Sierra Leone.

Liberia is closing some of its borders and screening all incoming and outgoing passengers for Ebola at its airports. The problem is that current tests detect Ebola only after a person shows symptoms, and most of the early symptoms are something you see in passengers all the time: fever, sore throat, chills, muscle aches and nausea.

How can those with the disease be helped?

While experimental vaccines exist, there are no licensed ones that get widespread use, according to the WHO.

The disease can be devastating and, ultimately, deadly in a few ways. It “disarms your immune system, (so it) cannot fight the virus,” CNN Chief Medical Correspondent Sanjay Gupta notes.

It also causes people to lose fluids, because of vomiting and diarrhea in addition to bleeding, as Ebola inhibits the blood’s ability to clot, adds Gupta.

The most important thing a person needs to do to survive is to get treated as early and effectively as possible.

But that’s not always easy in some parts of Africa, says Monia Sayah, a nurse with Doctors Without Borders.

“We go into communities where we are not necessarily welcome, because they understand now that the survival rate is not very high,” Sayah told CNN’s Anderson Cooper.

Sayah acknowledges that, in addition to immediate family members, health care workers are among those at highest risk of being infected. One need look no farther than Dr. Sheik Humarr Khan, a doctor who was on the front lines fighting the Ebola outbreak in Sierra Leone before dying this week from complications of the disease.

Health care workers don gowns, gloves and masks, and take other measures to guard against the disease.

“Every inch of the body has to be covered,” Sayah said. “It’s essential.”

What’s next?

A Canadian scientist who recently returned from the front lines of the West African Ebola outbreak says he hopes this is the last time the world has to combat the virus without specific treatments or protective vaccines.

Dr. Gary Kobinger, chief of special pathogens at Canada’s National Microbiology Laboratory in Winnipeg, suggested this outbreak — the largest on record — will speed efforts to get emergency use approvals for experimental vaccines and therapies in future Ebola epidemics.

“My really, really deepest wish — and I don’t want to call this a dream, because it’s not a dream — is that there won’t be another outbreak like this. (That) this is the last one. Next time, we’ll be ready,” Kobinger said in an interview Monday.

But Kobinger agreed with others in his field who have argued that it would be unwise to use these untested tools this time, saying the Ebola vaccines and drugs must go through Phase 1 clinical trials in people before they could be used in an outbreak setting. Phase 1 trials involve giving a drug or vaccine to a small number of healthy adult volunteers to ensure that it is safe for human use.

“These are all experimental drugs that have not met the requirements … even for a Phase 1 (trial) right now in humans. So they have to pass all the toxicity (tests), they have to pass the safety trials,” he said.

Identifying and isolating infected people is the primary function of response teams in Ebola outbreaks. With limited medical treatment to offer, the goal is to bring outbreaks to an end by stopping transmission.

Over the past 15 years or so the Winnipeg lab and several in the United States have made significant headway in developing Ebola vaccines and treatments that look highly promising when studied in non-human primates. The vaccines even appear to prevent death in some cases when given after exposure to the virus, if they are administered quickly enough.

But bringing these treatments to the field has proven to be difficult, with financial and regulatory hurdles frustrating the best efforts of the scientists involved.

The scale of this outbreak is renewing interest in breaking down those barriers, however. A number of experts are now talking of the need, once this outbreak is over, to chart a path so the next time there will be therapeutic options.