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Abbas Dulleh , AP
A health worker takes a man's temperature, center, before his is allowed to enter into a government building, with a message, right, reading 'Kindly wash your hands before entering' the building in Monrovia, Liberia, Thursday, Jan. 14, 2016. The World Health Organization declared an end to the deadliest Ebola outbreak ever on Thursday after no new cases emerged in Liberia, though health officials warn that it will be several more months before the world is considered free of the disease that claimed more than 11,300 lives over two years. (AP Photo/Abbas Dulleh)

DAKAR, Senegal — The World Health Organization announced Thursday that the world's biggest-ever Ebola epidemic is over after two years. Here is a closer look:

THE GRIM STATISTICS: At least 11,315 people died from Ebola: 4,809 deaths were reported in Liberia, while Sierra Leone recorded 3,955 deaths and at least 2,536 people perished in Guinea. Nigeria recorded eight deaths, and six others died in Mali. A handful of others died in Europe or the United States after being infected while in West Africa or treating patients some caregivers got sick and die in Europe while treating patients who got sick in Africa? sickened there.

SURVIVORS: There are more than 17,000 survivors of Ebola, most of who live in West African countries where there are few specialized treatment resources. Many of the survivors have vision and hearing issues. Some others experience physical and emotional pains, fatigue and other problems. A number of female survivors also have suffered miscarriages or had stillborn children for reasons that are still not clear.

LESSONS LEARNED: WHO has acknowledged there was a "failure to see that conditions for explosive spread were present right at the start," according to a draft internal document obtained by AP. WHO blamed incompetent staff and said it let bureaucratic bungles delay people and delivery of money to fight the virus. The document said the agency was hampered by budget cuts and the need to battle other diseases flaring around the world. Health experts though also say they underestimated how difficult it would be to change behavior — people were afraid to send their relatives to treatment centers and began hiding sick people in their homes. Others defied quarantines and traveled when sick, or continued traditional burial practices that allowed the disease to continue spreading.

THE UNKNOWNS: Scientists are still learning more about the long-term effects of Ebola and also about the longevity of the virus in survivors. WHO says it's possible in rare instances for patients who survived Ebola to develop the lethal disease again, when the virus lingering in the body starts to replicate at high levels. Ebola can remain in the semen of male survivors for up to a year, according to WHO. This means on rare occasions that men who have recovered can still infect their partners, experts say.

COULD IT HAPPEN AGAIN?: WHO officials acknowledge it's possible: Already there have been 10 flare-ups through the region in areas thought to be clear of Ebola. However, WHO says the areas are significantly more prepared to tackle future outbreaks. Early warning systems are in place, along with stockpiles of protective gear. People living in these countries also know what steps they can take immediately to avoid getting sick after lengthy public awareness campaigns. Ebola is often spread to people from wild animals, thought to include bats and monkeys; the natural reservoir has not yet been identified.

AP Medical Writer Maria Cheng contributed to this report.