Ebola Fast FactsCNN LibraryUpdated 5:32 PM ET, Wed February 25, 2015Photos: The Ebola epidemic 47 photosThe Ebola epidemic – Red Cross workers, wearing protective suits, carry the body of a person who died from Ebola during a burial in Monrovia, Liberia, on Monday, January 5. Since the epidemic started a little more than a year ago in a remote village in Guinea, the world has seen more than 8,400 deaths, according to the latest numbers from the World Health Organization. And that number is believed to be low, since there was widespread under-reporting of cases, according to WHO.Hide Caption 1 of 47Photos: The Ebola epidemic 47 photosPauline Cafferkey, a Scottish woman diagnosed with Ebola, is put on a plane in Glasgow, Scotland, on Tuesday, December 30. Cafferkey, a 39-year-old nurse who volunteered in Sierra Leone, was being transported to London for treatment.Hide Caption 2 of 47Photos: The Ebola epidemic 47 photosLiberian President Ellen Johnson Sirleaf has her temperature taken before the opening of a new Ebola clinic Tuesday, November 25, in Monrovia.Hide Caption 3 of 47Photos: The Ebola epidemic 47 photosA child who survived the Ebola virus is fed by another survivor at a treatment center on the outskirts of Freetown, Sierra Leone, on Tuesday, November 11.Hide Caption 4 of 47Photos: The Ebola epidemic 47 photosHealth workers in Monrovia cover the body of a man suspected of dying from the Ebola virus on Friday, October 31.Hide Caption 5 of 47Photos: The Ebola epidemic 47 photosKaci Hickox leaves her home in Fort Kent, Maine, to take a bike ride with her boyfriend on Thursday, October 30. Hickox, a nurse, recently returned to the United States from West Africa, where she treated Ebola victims. State authorities wanted her to avoid public places for 21 days -- the virus' incubation period. But Hickox, who twice tested negative for Ebola, said she would defy efforts to keep her quarantined at home.Hide Caption 6 of 47Photos: The Ebola epidemic 47 photosCrew members at an airport in Accra, Ghana, unload supplies sent from China on Wednesday, October 29.Hide Caption 7 of 47Photos: The Ebola epidemic 47 photosHealth officials in Nairobi, Kenya, prepare to screen passengers arriving at the Jomo Kenyatta International Airport on Tuesday, October 28.Hide Caption 8 of 47Photos: The Ebola epidemic 47 photosU.S. President Barack Obama hugs Ebola survivor Nina Pham in the Oval Office of the White House on Friday, October 24. Pham, one of two Dallas nurses diagnosed with the virus, was declared Ebola-free after being treated at a hospital in Bethesda, Maryland. The other nurse, Amber Vinson (not pictured), was treated in Atlanta and also declared Ebola-free.Hide Caption 9 of 47Photos: The Ebola epidemic 47 photosHealth workers in Port Loko, Sierra Leone, transport the body of a person who is suspected to have died of Ebola on Tuesday, October 21.Hide Caption 10 of 47Photos: The Ebola epidemic 47 photosHealth workers bury a body on the outskirts of Monrovia on Monday, October 20.Hide Caption 11 of 47Photos: The Ebola epidemic 47 photosGarteh Korkoryah, center, is comforted during a memorial service for her son, Thomas Eric Duncan, on Saturday, October 18, in Salisbury, North Carolina. Duncan, a 42-year-old Liberian citizen, died October 8 in a Dallas hospital. He was in the country to visit his son and his son's mother, and he was the first person in the United States to be diagnosed with Ebola.Hide Caption 12 of 47Photos: The Ebola epidemic 47 photosBoys run from blowing dust as a U.S. military aircraft leaves the construction site of an Ebola treatment center in Tubmanburg, Liberia, on Wednesday, October 15.Hide Caption 13 of 47Photos: The Ebola epidemic 47 photosAid workers from the Liberian Medical Renaissance League stage an Ebola awareness event October 15 in Monrovia. The group performs street dramas throughout Monrovia to educate the public on Ebola symptoms and how to handle people who are infected with the virus.Hide Caption 14 of 47Photos: The Ebola epidemic 47 photosEbola survivors prepare to leave a Doctors Without Borders treatment center after recovering from the virus in Paynesville, Liberia, on October 12.Hide Caption 15 of 47Photos: The Ebola epidemic 47 photosA woman crawls toward the body of her sister as a burial team takes her away for cremation Friday, October 10, in Monrovia. The sister had died from Ebola earlier in the morning while trying to walk to a treatment center, according to her relatives.Hide Caption 16 of 47Photos: The Ebola epidemic 47 photosA person peeks out from the Dallas apartment where Thomas Eric Duncan, the first person diagnosed with the Ebola virus in the United States, was staying on Friday, October 3.Hide Caption 17 of 47Photos: The Ebola epidemic 47 photosA girl cries as community activists approach her outside her Monrovia home on Thursday, October 2, a day after her mother was taken to an Ebola ward.Hide Caption 18 of 47Photos: The Ebola epidemic 47 photosA health official uses a thermometer Monday, September 29, to screen a Ukrainian crew member on the deck of a cargo ship at the Apapa port in Lagos, Nigeria.Hide Caption 19 of 47Photos: The Ebola epidemic 47 photosWorkers move a building into place as part of a new Ebola treatment center in Monrovia on September 28.Hide Caption 20 of 47Photos: The Ebola epidemic 47 photosMedical staff members at the Doctors Without Borders facility in Monrovia burn clothes belonging to Ebola patients on Saturday, September 27. Hide Caption 21 of 47Photos: The Ebola epidemic 47 photosMedics load an Ebola patient onto a plane at Sierra Leone's Freetown-Lungi International Airport on Monday, September 22.Hide Caption 22 of 47Photos: The Ebola epidemic 47 photosA few people are seen in Freetown during a three-day nationwide lockdown on Sunday, September 21. In an attempt to curb the spread of the Ebola virus, people in Sierra Leone were told to stay in their homes.Hide Caption 23 of 47Photos: The Ebola epidemic 47 photosSupplies wait to be loaded onto an aircraft at New York's John F. Kennedy International Airport on Saturday, September 20. It was the largest single shipment of aid to the Ebola zone to date, and it was coordinated by the Clinton Global Initiative and other U.S. aid organizations.Hide Caption 24 of 47Photos: The Ebola epidemic 47 photosA child stops on a Monrovia street Friday, September 12, to look at a man who is suspected of suffering from Ebola.Hide Caption 25 of 47Photos: The Ebola epidemic 47 photosHealth workers in Monrovia place a corpse into a body bag on Thursday, September 4.Hide Caption 26 of 47Photos: The Ebola epidemic 47 photosAfter an Ebola case was confirmed in Senegal, people load cars with household items as they prepare to cross into Guinea from the border town of Diaobe, Senegal, on Wednesday, September 3.Hide Caption 27 of 47Photos: The Ebola epidemic 47 photosCrowds cheer and celebrate in the streets Saturday, August 30, after Liberian authorities reopened the West Point slum in Monrovia. The military had been enforcing a quarantine on West Point, fearing a spread of the Ebola virus.Hide Caption 28 of 47Photos: The Ebola epidemic 47 photosA health worker wearing a protective suit conducts an Ebola prevention drill at the port in Monrovia on Friday, August 29. Hide Caption 29 of 47Photos: The Ebola epidemic 47 photosVolunteers working with the bodies of Ebola victims in Kenema, Sierra Leone, sterilize their uniforms on Sunday, August 24. Hide Caption 30 of 47Photos: The Ebola epidemic 47 photosA burial team from the Liberian Ministry of Health unloads bodies of Ebola victims onto a funeral pyre at a crematorium in Marshall, Liberia, on Friday, August 22.Hide Caption 31 of 47Photos: The Ebola epidemic 47 photosDr. Kent Brantly leaves Emory University Hospital on Thursday, August 21, after being declared no longer infectious from the Ebola virus. Brantly was one of two American missionaries brought to Emory for treatment of the deadly virus.Hide Caption 32 of 47Photos: The Ebola epidemic 47 photosAn Ebola Task Force soldier beats a local resident while enforcing a quarantine on the West Point slum on August 20.Hide Caption 33 of 47Photos: The Ebola epidemic 47 photosLocal residents gather around a very sick Saah Exco, 10, in a back alley of the West Point slum on Tuesday, August 19. The boy was one of the patients that was pulled out of a holding center for suspected Ebola patients after the facility was overrun and closed by a mob on August 16. A local clinic then refused to treat Saah, according to residents, because of the danger of infection. Although he was never tested for Ebola, Saah's mother and brother died in the holding center.Hide Caption 34 of 47Photos: The Ebola epidemic 47 photosA burial team wearing protective clothing retrieves the body of a 60-year-old Ebola victim from his home near Monrovia on Sunday, August 17. Hide Caption 35 of 47Photos: The Ebola epidemic 47 photosWorkers prepare the new Ebola treatment center on August 17.Hide Caption 36 of 47Photos: The Ebola epidemic 47 photosLiberian police depart after firing shots in the air while trying to protect an Ebola burial team in the West Point slum of Monrovia on August 16. A crowd of several hundred local residents reportedly drove away the burial team and their police escort. The mob then forced open an Ebola isolation ward and took patients out, saying the Ebola epidemic is a hoax.Hide Caption 37 of 47Photos: The Ebola epidemic 47 photosA crowd enters the grounds of an Ebola isolation center in the West Point slum on August 16. The mob was reportedly shouting, "No Ebola in West Point."Hide Caption 38 of 47Photos: The Ebola epidemic 47 photosA health worker disinfects a corpse after a man died in a classroom being used as an Ebola isolation ward Friday, August 15, in Monrovia.Hide Caption 39 of 47Photos: The Ebola epidemic 47 photosHealth workers in Kenema screen people for the Ebola virus on Saturday, August 9, before they enter the Kenema Government Hospital.Hide Caption 40 of 47Photos: The Ebola epidemic 47 photosAid worker Nancy Writebol, wearing a protective suit, gets wheeled on a gurney into Emory University Hospital in Atlanta on August 5. A medical plane flew Writebol from Liberia to the United States after she and her colleague Dr. Kent Brantly were infected with the Ebola virus in the West African country. Hide Caption 41 of 47Photos: The Ebola epidemic 47 photosMembers of Doctors Without Borders adjust tents in the isolation area in Kailahun on July 20.Hide Caption 42 of 47Photos: The Ebola epidemic 47 photosBoots dry in the Ebola treatment center in Kailahun on July 20.Hide Caption 43 of 47Photos: The Ebola epidemic 47 photosDr. Jose Rovira of the World Health Organization takes a swab from a suspected Ebola victim in Pendembu, Sierra Leone, on Friday, July 18.Hide Caption 44 of 47Photos: The Ebola epidemic 47 photosRed Cross volunteers disinfect each other with chlorine after removing the body of an Ebola victim from a house in Pendembu on July 18.Hide Caption 45 of 47Photos: The Ebola epidemic 47 photosA scientist separates blood cells from plasma cells to isolate any Ebola RNA and test for the virus Thursday, April 3, at the European Mobile Laboratory in Gueckedou, Guinea.Hide Caption 46 of 47Photos: The Ebola epidemic 47 photosHealth specialists work Monday, March 31, at an isolation ward for patients at the facility in southern Guinea.Hide Caption 47 of 47 (CNN)Here's some background information about Ebola, a virus with a high fatality rate that was first identified in Africa in 1976.Facts:Ebola hemorrhagic fever is a disease caused by one of five different Ebola viruses. Four of the strains can cause severe illness in humans and animals. The fifth, Reston virus, has caused illness in some animals, but not in humans. The first human outbreaks occurred in 1976, one in northern Zaire (now Democratic Republic of the Congo) in Central Africa: and the other, in southern Sudan (now South Sudan). The virus is named after the Ebola River, where the virus was first recognized in 1976, according to the Centers for Disease Control and Prevention.Ebola is extremely infectious but not extremely contagious. It is infectious, because an infinitesimally small amount can cause illness. Laboratory experiments on nonhuman primates suggest that even a single virus may be enough to trigger a fatal infection.Instead, Ebola could be considered moderately contagious, because the virus is not transmitted through the air. The most contagious diseases, such as measles or influenza, virus particles are airborne.Humans can be infected by other humans if they come in contact with body fluids from an infected person or contaminated objects from infected persons. Humans can also be exposed to the virus, for example, by butchering infected animals.While the exact reservoir of Ebola viruses is still unknown, researchers believe the most likely natural hosts are fruit bats. Symptoms of Ebola typically include: weakness, fever, aches, diarrhea, vomiting and stomach pain. Additional experiences include rash, red eyes, chest pain, throat soreness, difficulty breathing or swallowing and bleeding (including internal).Typically, symptoms appear 8-10 days after exposure to the virus, but the incubation period can span two to 21 days.Unprotected health care workers are susceptible to infection because of their close contact with patients during treatment.Ebola is not transmissible if someone is asymptomatic or once someone has recovered from it. However, the virus has been found in semen for up to three months. Deadly human Ebola outbreaks have been confirmed in the following countries: Democratic Republic of the Congo (DRC), Gabon, South Sudan, Ivory Coast, Uganda, Republic of the Congo (ROC), Guinea and Liberia. According to the World Health Organization, "there is no specific treatment or vaccine," and the fatality rate can be up to 90%. Patients are given supportive care, which includes providing fluids and electrolytes and food.There are five subspecies of the Ebola virus: Zaire ebolavirus (EBOV), Bundibugyo ebolavirus (BDBV), Sudan ebolavirus (SUDV), Taï Forest ebolavirus (TAFV) and Reston ebolavirus (RESTV)Click here for the CDC's list of known cases and outbreaks. 2014-2015 West Africa Outbreak:(Full historical timeline at bottom)Cases listed below include confirmed, probable or suspected cases of Ebola as of February 22, 2015 (World Health Organization and CDC):Guinea - 3155 cases, 2091 deathsLiberia - 9238 cases, 4037 deathsMali - 8 cases, 6 deaths Nigeria - 20 cases, 8 deaths Senegal - 1 case, 0 deaths (infection originated in Guinea)Sierra Leone - 11301 cases, 3461 deathsSpain - 1 case, 0 deathsUnited Kingdom - 1 case, 0 deathsUnited States - 4 cases, 1 death (two infections originated in the United States, one in Liberia and one in Guinea)March 25, 2014 - The CDC issues its initial announcement on an outbreak in Guinea, and reports of cases in Liberia and Sierra Leone. "In Guinea, a total of 86 suspected cases, including 59 deaths (case fatality ratio: 68.5%), had been reported as of March 24, 2014. Preliminary results from the Pasteur Institute in Lyon, France suggest Zaire ebolavirus as the causative agent."April 16, 2014 - The New England Journal of Medicine publishes a report, speculating that the current outbreak's Patient Zero was a two-year-old from Guinea. The child died on December 6, 2013, followed by his mother, sister and grandmother over the next month. July 2014 - Patrick Sawyer, a top government official in the Liberian Ministry of Finance, dies at a local Nigerian hospital. He is the first American to die in what officials are calling "deadliest Ebola outbreak in history."July 2014 - Nancy Writebol, an American aid worker in Liberia, tests positive for Ebola. According to Samaritan's Purse, Writebol is infected while treating Ebola patients in Liberia. July 26, 2014 - Kent Brantly, medical director for Samaritan Purse's Ebola Consolidated Case Management Center in Liberia, is infected with the virus. According to Samaritan's Purse, Brantly is infected while treating Ebola patients. July 29, 2014 - According to Doctors Without Borders, Dr. Sheik Humarr Khan who was overseeing Ebola treatment at Kenema Government Hospital in Sierra Leone dies from complications of the disease. July 30, 2014 - The Peace Corps announces it is removing its volunteers from Liberia, Sierra Leone and Guinea. July 31, 2014 - CDC raises its warning to Level 3. It warns U.S. residents to avoid "nonessential travel" to Sierra Leone, Guinea, and Liberia. August 2, 2014 - A specially equipped medical plane carrying Ebola patient Dr. Kent Brantly lands at Dobbins Air Reserve Base in Marietta, Georgia. He is then driven by ambulance to Emory University Hospital in Atlanta.August 4, 2014 - CNN reports that three top secret, experimental vials of the drug, "ZMapp," were flown into Liberia last week in a last-ditch effort to save Brantly and Writebol, according to a source familiar with details of the treatment. Doctors report "significant improvement."August 6, 2014 - Nancy Writebol arrives at Emory in Atlanta for treatment.August 8, 2014 - Experts at the World Health Organization declare the Ebola epidemic ravaging West Africa an international health emergency that requires a coordinated global approach, describing it as the worst outbreak in the four-decade history of tracking the disease.August 19, 2014 - Liberia's President Ellen Johnson Sirleaf declares a nationwide curfew beginning August 20 and orders two communities to be completely quarantined, with no movement in or out of the areas. August 21, 2014 - Dr. Kent Brantly is discharged from Emory University Hospital. It is also announced that Nancy Writebol had been released on Tuesday, August 19. The releases come after Emory staff are confident Brantly and Writebol pose "no public health threat."September 6, 2014 - The government of Sierra Leone announces plans for a nationwide lockdown from September 19-21, in order to stop the spread of Ebola. The lockdown is being billed as a predominantly social campaign rather than a medical one, in which volunteers will go door-to-door to talk to people.September 16, 2014 - President Barack Obama calls the efforts to combat the Ebola outbreak centered in West Africa "the largest international response in the history of the CDC." Speaking from the CDC headquarters in Atlanta, Obama adds that "faced with this outbreak, the world is looking to" the United States to lead international efforts to combat the virus. He says the United States is ready to take on that leadership role.September 30, 2014 - Dr. Thomas Frieden, director of the CDC, announces the first diagnosed case of Ebola in the United States. The person has been hospitalized and isolated at Texas Health Presbyterian Hospital in Dallas, Texas, since September 28.October 1, 2014 - Liberian government officials release the name of the first diagnosed case of Ebola in the United States: Thomas Eric Duncan.October 6, 2014 - A nurse's assistant in Spain becomes the first person known to have contracted Ebola outside Africa in the current outbreak. The woman helped treat two Spanish missionaries, both of whom had contracted Ebola in West Africa, one in Liberia and the other in Sierra Leone. Both died after returning to Spain. On October 19, Spain's Special Ebola Committee says that nurse's aide Teresa Romero Ramos is considered free of the Ebola virus.October 6, 2014 - NBC freelance cameraman Ashoka Mukpo arrives at Nebraska Medical Center for treatment after contracting Ebola in Liberia. On October 21, the hospital says that Mukpo no longer has the Ebola virus in his bloodstream and will be allowed to leave.October 8, 2014 - Thomas Eric Duncan dies of Ebola in Dallas.October 11, 2014 - Nina Pham, a Dallas nurse who cared for the now-deceased Ebola patient Thomas Eric Duncan, tests positive for Ebola during a preliminary blood test. She is the first person to contract Ebola on American soil.October 15, 2014 - Amber Vinson, a second Dallas nurse who also cared for Thomas Eric Duncan, is diagnosed with Ebola. Authorities say Vinson flew on a commercial jet from Cleveland to Dallas days before testing positive for Ebola.October 20, 2014 - Under fire in the wake of Ebola cases involving two Dallas nurses, the CDC issues updated Ebola guidelines that stress the importance of more training and supervision, and recommend that no skin be exposed when workers are wearing personal protective equipment, or PPE.October 23, 2014 - Craig Spencer, a 33 year-old doctor who recently returned from Guinea has tested positive for Ebola -- the first case of the deadly virus in New York City and the fourth diagnosed in the United States.October 24, 2014 - The National Institutes of Health announces one of the Dallas nurses, Nina Pham, has been declared free of the Ebola virus. Doctors at Emory University Hospital say tests no longer detect the virus in the blood of the other nurse, Amber Vinson. Pham is released from a Maryland hospital on October 24, and Vinson is released from an Atlanta hospital on October 28.October 24, 2014 - In response to the New York Ebola case, the governors of New York and New Jersey announce that their states were stepping up airport screening beyond federal requirements for travelers from West Africa. The new protocol mandates a quarantine for any individual, including medical personnel, who has had direct contact with individuals infected with Ebola while in Liberia, Sierra Leone, or Guinea. The policy allows the states to determine hospitalization or quarantine for up to 21 days for other travelers from affected countries.November 5, 2014 - Nurse's aide Maria Teresa Romero Ramos, believed to be the first person to contract Ebola outside of Africa, is released from the hospital in Madrid, Spain.November 11, 2014 - Dr. Craig Spencer, the first person to test positive for Ebola in New York City, is released from Bellevue Hospital. With Spencer free of the virus, all U.S. patients who had Ebola have recovered.November 15, 2014 - Dr. Martin Salia, who became infected with Ebola while treating patients in Sierra Leone, arrives at Nebraska Medical Center in Omaha. Salia, a native of Sierra Leone, is a legal permanent resident of the United States married to a U.S. citizen. November 17, 2014 - Dr. Salia dies at Nebraska Medical Center. December 24, 2014 - The CDC announces that a technician will be monitored for three weeks after possibly being exposed to the Ebola virus at one of the agency's Atlanta labs. The agency reports a small amount of material which may have contained the live virus had been mistakenly transferred from one lab to another.January 18, 2015 - Mali is declared Ebola free after no new cases in 42 days.February 22, 2015 - Liberia reopens its land border crossings shut down during the Ebola outbreak, and Liberian President Ellen Johnson Sirleaf also lifts a nationwide curfew imposed in August to help combat the virus.Historical Timeline: *Includes outbreaks resulting in more than 100 deaths or special cases. 1976 - First recognition of the EBOV disease is in Zaire (now Democratic Republic of the Congo). The outbreak has 318 reported human cases, leading to 280 deaths. An SUDV outbreak also occurs in Sudan (now South Sudan), which incurs 284 cases and 151 deaths. 1989 - In Reston, Virginia, macaque monkeys imported from the Philippines are found to be infected with the Ebola virus (later named the Ebola-Reston virus).1990 - In Texas and Virginia quarantine facilities, four humans develop Ebola antibodies after contact with monkeys imported from the Philippines. None of the humans has symptoms. 1995 - An outbreak in Democratic Republic of the Congo (formerly Zaire) leads to 315 reported cases and at least 250 deaths. 2000-2001 - A Ugandan outbreak (SUDV) results in 425 human cases and 224 deaths. 2001-2002 - An EBOV outbreak occurs on the border of Gabon and Republic of the Congo (ROC), which results in 53 deaths on the Gabon side and at least 43 deaths on the Republic of the Congo side. December 2002-April 2003 - An EBOV outbreak in Republic of the Congo results in 143 reported cases and 128 deaths. 2007 - An EBOV outbreak occurs in the Democratic Republic of the Congo (DRC), 187 of the 264 cases reported result in death. In late 2007, an outbreak in Uganda leads to 37 deaths. 149 cases were reported.November 2008 - The Ebola-Reston virus (RESTV) is detected in five humans in the Philippines. They are workers on a pig farm and slaughterhouse and suffer no symptoms. This is the first known occurrence of the Reston virus in pigs. August 26, 2014 - The Ministry of Health in the Democratic Republic of the Congo notifies the World Health Organization of an Ebola outbreak in the country. It is the seventh outbreak in the country since 1976, when the virus was first identified near the Ebola river. The outbreak is not related to the ongoing outbreak in Guinea, Liberia, Nigeria and Sierra Leone. November 21, 2014 - The World Health Organization declares an end to the Ebola outbreak in the Democratic Republic of Congo. A total of 66 cases and 49 deaths were recorded. More from HealthCan you find the 'best' hospital for you?Educación: clave del futuro¿La eutanasia es un derecho?