New Ebola cases in West Africa at lowest weekly level in a year: WHO
UN health agency calls situation encouraging, notes officials unable to track where virus spreading
The World Health Organization says the number of Ebola cases reported in Guinea and Sierra Leone last week dropped to 18, the lowest total this year.
In an update published this week, the UN health agency said the situation was "encouraging" but noted officials are still unable to track exactly where the virus is spreading.
In Guinea, five of the country's nine new cases were detected only after the patients died; none had sought treatment in a hospital. In Sierra Leone, only two of the nine cases were identified as contacts of previous Ebola patients.
In Liberia, the outbreak will be declared over on May 9 unless any new cases are announced. Some experts warn no country will be safe until the entire region wipes out Ebola
To date, WHO estimates Ebola has killed more than 11,000 people, the vast majority in West Africa.
With files from The Associated Press