WHO announced the Ebola outbreak - the largest and longest in history - is worrying enough to merit being declared an international health emergency. WHO declared similar emergencies for the swine flu pandemic in 2009 and for polio in May.
This agency had convened an expert committee this week to assess the severity of the ongoing epidemic in West Africa.
The current outbreak of Ebola began in Guinea in March and has since spread to Sierra Leone and Liberia. There is no licensed treatment or vaccine for Ebola and the death rate has been about 50 percent.