Geneva, October 18 (RHC), -- 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.

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

In the United States, President Baracdk Obama continues to oppose a travel ban on travelers traveling from areas affected by the Ebola epidemic, but now says he will not rule one out.