In the years since Ebola's discovery in 1976, there have been intermittent outbreaks of the disease — but none nearly as deadly or far-reaching as the current crisis, which has been centred in three West African countries: Liberia, Sierra Leone and Guinea.
The Ebola outbreak has claimed more than 8,600 lives since the first cases were detected in West Africa. New cases are still being reported, but the number is shrinking, and the World Health Organization says progress has been made in detecting, isolating and caring for people infected with the virus.
Here's what you need to know about the disease and the effort to stop its spread.
How many people have died?
The World Health Organization and a UN mission formed to respond to the crisis have been working with health officials on the ground to tally the number of people who die of Ebola.
According to a Jan. 21 WHO report, there have been more than 21,000 "confirmed, probable and suspected" cases of Ebola and more than 8,600 deaths in the three hardest-hit West African countries since the outbreak began. Those figures likely understate the actual numbers, as it's believed that not all cases are detected and reported.
Who is at greatest risk?
Liberia, Sierra Leone and Guinea have faced what the WHO has described as the most "widespread and intense" transmission of the disease. People living in the most affected areas were urged to learn to identify symptoms and report every case, while international organizations scrambled to assist health ministries and support overwhelmed local health systems.
Liberian President Ellen Johnson Sirleaf, who spoke to CBC News as her country battled the outbreak last year, said Ebola was like an "unknown enemy" that descended on a country that was already struggling with a weak health-care system staffed by too few doctors.
After months of stepped-up efforts, even the hardest-hit communities are now seeing signs of progress. The most recent report from WHO says the number of newly reported cases is falling in Guinea, Liberia and Sierra Leone.
In Liberia, a health official announced on Jan. 23 that there were just five remaining confirmed cases in the country.
"It means that we are going down to zero, if everything goes well, if other people don't get sick in other places," said Deputy Health Minister Tolbert Nyenswah, who heads Liberia's Ebola task force.
Health professionals have been particularly vulnerable to Ebola, which is transmitted through "direct contact with body fluids of a person who has symptoms of Ebola disease," the U.S. Centers for Disease Control and Prevention says.
CBC's Adrienne Arsenault visited a clinic treating Ebola patients in Liberia.
"Doctors died, nurses died, physician assistants died — they were the first to take the toll," the Liberian president said last year in a wide-ranging interview with the CBC about her country's response to the disease.
The safe recovery and disposal of the bodies of Ebola patients has also been a challenge, particularly in some affected areas where family members generally wash the body of a loved one.
Health workers in hard-hit areas had expressed concern about both safety and pay, and in mid-December it was announced that workers in Sierra Leone would receive hazard pay electronically to compensate them for their efforts on the front lines of fighting Ebola.
What's being done to slow Ebola's spread?
Health officials in affected areas have been intensely focused on identifying and containing cases through increased surveillance and better treatment facilities. The stepped-up efforts have proved successful — Nigeria and Senegal were declared free of Ebola last year, and more recently, Mali was reported to be disease-free.
In hospitals and treatment centres, people working with Ebola patients have been urged to follow rigid protocols and wear elaborate personal protective equipment to protect themselves.
People flying out of affected areas face temperature screenings and questionnaires, and some countries — including Canada — have enhanced airport screening for inbound travellers coming from affected areas.
The search for treatment or a cure is also moving forward. While there are no proven treatments for Ebola patients, researchers are working on several possibilities, including a vaccine developed in Canada.
How is Canada preparing?
Health officials have repeatedly said the risk to Canadians is very low, but public health agencies, hospitals and staff are still preparing for possible cases.
Canada has also mirrored the U.S. in creating a "rapid response team" that will be deployed to hospitals to help local officials with:
- Implementing containment protocols.
- Contact tracing.
- Lab expertise.
- Proper use of personal protective equipment.
- Providing necessary supplies, including face shields and gloves.
How much more is needed?
The UN has been calling for increased funding throughout the crisis, most recently asking for $1 billion for the first six months of 2015 as the hardest-hit countries try to stamp out new cases. Much of that funding will go to running existing programs, boosting surveillance and tracking cases, as health officials try to identify and respond to each and every remaining case.
Pleased to see signs of reduction of #ebola in affected West African countries. Extraordinary how the world came together to support— @ValerieAmos
Valerie Amos, UN emergency relief co-ordinator, has said she's pleased with the progress, but she warns against complacency in the weeks and months ahead.
Liberia's president warned world leaders of the human and economic toll of the disease, saying "across West Africa, a generation of young people risk being lost to an economic catastrophe."
The outbreak has battered the economies of affected countries, as travel restrictions, quarantines and general fears about the disease slowed economic growth.
A UN forum that looked at the effect of Ebola on the West African nations recently urged creditors to consider debt forgiveness as a way to help Sierra Leone, Guinea and Liberia cope with the demands of containing the Ebola outbreak.