The World Health Organization says it is focusing efforts on 15 African countries to prevent the spread of the growing Ebola outbreak from Liberia, Sierra Leone and Guinea. The official toll in those countries surpassed 4,500 this week. Of the 15 at-risk countries, WHO global director Isabelle Nuttall said Mali and the Ivory Coast are the most vulnerable.

Dr. Isabelle Nuttall: “We have identified both Mali and Côte d’Ivoire as the two top priorities country. A team is being assembled to go there and do a real thorough assessment; but more than an assessment, it’s moving from an assessment into making sure that things are in place.”

On Thursday, Jamaica has become the latest country to impose a travel ban on passengers from Liberia, Guinea and Sierra Leone.