The organization stopped short of saying there should be general international travel or trade bans, but acknowledged that the outbreak, already in its sixth month, was far from being contained.
One major international medical organisation, Doctors Without Borders, responded to the statement with a renewed call for massive deployment of health specialists to stricken countries. Lives are being lost because the response is too slow, it said.
Margaret Chan, WHOs director general, told a news conference at the bodys Geneva headquarters: This is the largest, most severe, most complex outbreak in the nearly four-decade history of the disease.
I am declaring the current outbreak of the Ebola virus disease a public health emergency of international concern, she added. Countries affected to date simply dont have the capacity to manage an outbreak on this scale on their own.
WHO urged all states where the disease is spreading to declare a state of emergency, to screen all people leaving at international airports, seaports and land crossings, and to prevent travel by anyone suspected of having the Ebola virus. But the organization did not recommend a ban on travel to or from places with outbreaks due to low risk of infection.
According to figures released by the WHO this week, the virus has claimed 932 lives since March. Most of the cases are in Guinea, Liberia and Sierra Leone, but nine cases have also been reported in Nigeria.
- ALAN COWELL