One year after the emergence of the deadly Ebola virus in West Africa that has killed more than 10,000, a top United Nations health official says the outbreak could end this summer.
While cases are still being confirmed in Guinea, Liberia and Sierra Leone, the hardest hit countries, the last few months have seen a substantial decline in the overall number of cases, says Ismail Ould Cheikh Ahmed, the head of the United Nations Mission for Ebola Emergency Response.
The requirement for classifying a country as "Ebola-free" is for 42 days - twice the incubation period of the virus - to pass with no new cases.
Unfortunately, last week Liberia recorded its first new case in more than 2 weeks, while in Guinea cases are increasing after a reduction at the beginning of the year. The medical charity Doctors Without Borders says overall cases have not declined significantly since January.
Still, there is hope the outbreak could be considered over in the coming months, almost certainly by August, Ahmed says.
"We have been running away from giving any specific date, but I am pretty sure myself that it will be gone by the summer," he says.
Exactly one year ago the World Health Organization officially announced an outbreak of Ebola beginning in Guinea, where 49 cases and 29 deaths had been reported.
Since then the disease has infected more than 24,000 people.
Ahmed acknowledged that the United Nations had made mistakes in its early handling of the crisis.
"There was probably a lack of knowledge and there was a certain degree of arrogance, but I think we are learning lessons," he said.
Doctors Without Borders says its early calls for help were ignored by what it termed a "global coalition of inaction" by both local governments and WHO.
"And of course it was frustrating that we weren't heard and that has probably led to the scale of the epidemic we see today," says Henry Gary, the charity's emergency coordinator.
Following WHO's initial announcement of the outbreak, 5 months would pass before the agency declared it a public health emergency of international concern.
Researchers now believe the first person to contract the disease - a 2-year-old boy living in a village in southern Guinea - did so in December 2013, 3 months before the WHO announcement.
The disease not only killed the boy, Emile Ouamouno, but it claimed the lives of his mother, sister and grandmother.
Researchers say they suspect the virus began to spread widely as people who attended the grandmother's funeral returned to their homes and other villages.
People are infected with the Ebola virus by direct contact through broken skin or the mouth and nose with the fluids of someone with Ebola, or through direct contact with contaminated bedding, clothing and surfaces. It can take up anywhere from two to 21 days for humans with the virus to show symptoms, and those infected aren't contagious until the symptoms develop.
Early symptoms include a sudden fever, muscle pain, fatigue, headache and sore throat, followed by vomiting, diarrhea, a rash and bleeding from the gums, eyes, nose and in the stools. Patients tend to die from dehydration and multiple organ failure.
There is no proven cure for Ebola, but vaccines are being tested on humans in trials, as well as blood products from someone who has survived the virus. Ill patients need to be rehydrated quickly using intravenous fluids, and they should be isolated from other people while being treated to prevent spread of the disease.
