UN tally of Ebola deaths passes 10,000, most in West Africa

GENEVA -- The World Health Organization marked a grim milestone Thursday in the biggest-ever Ebola outbreak, estimating the virus had killed over 10,000 people, mostly in the West African nations of Guinea, Liberia and Sierra Leone.

Fifteen other Ebola deaths also occurred in Mali, Nigeria and the United States.

When Ebola was detected in March 2014 in Guinea's forest, officials assumed the deadly virus could be stamped out quickly, just as it had in more than two dozen previous outbreaks, mostly in central and eastern Africa. But health officials acknowledge they were too slow to respond to this emergency, allowing Ebola to cross porous borders in a region where broken health systems were unable to stop its spread.

A huge global response -- including soldiers sent by Britain, the U.S. and other nations -- has slowed the deaths from Ebola dramatically, especially in Liberia, but the virus appears stubbornly entrenched in parts of Guinea and Sierra Leone.

The WHO declared Ebola an international health emergency in August, but critics have slammed the agency for waiting until there were nearly 1,000 deaths to do so. The WHO recently announced it was forming an independent expert panel to assess its response. Ebola cases also emerged elsewhere in Africa, including Nigeria, Senegal and Mali, and a few cases later were identified in the U.S. and Spain.

Liberia, once the hardest-hit country in the Ebola outbreak, released its last Ebola patient March 5. It has begun a 42-day countdown, and if no new cases are found in that period, it will be declared Ebola-free, according to WHO standards. To mark the epidemic's downturn, Liberian President Ellen Johnson-Sirleaf re-opened the country's borders with neighboring countries. Ambulances in Liberia also have been dispatched to help stop Ebola in Sierra Leone, and the government recently bought a 25-acre plot of land outside the capital to bury Ebola victims.

Both Guinea and Sierra Leone are reporting dozens of new cases every week, and the number of Ebola deaths taking place outside hospitals remains high, suggesting people are wary of seeking help or are hiding cases.

In both countries, there are still regular attacks against Western aid workers, and officials are unable to track where the Ebola virus is spreading.

Dr. Bruce Aylward, who is leading the WHO's Ebola response, said scientists sometimes have been tracking the wrong people when looking for potential Ebola cases.

He noted West Africa's upcoming rainy season -- beginning in April -- may make it difficult to get into remote areas.

The outbreak has had one silver lining: It has sped up the development of Ebola vaccines and treatments, something researchers have been working on for years.

The WHO and its partners have started testing two experimental shots, including a large-scale study to see whether a vaccine can help protect people exposed to the virus who haven't yet developed the disease.

Jonathan Paye-Layleh in Monrovia, Liberia, contributed to this report.