The World Health Organisation (WHO) has declared the Ebola outbreak to be an international public health emergency that requires an extraordinary response, as a Spanish priest who was infected with the disease was treated in Madrid.
The 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.
WHO chief Dr Margaret Chan said the announcement is "a clear call for international solidarity".
"Countries affected to date simply do not have the capacity to manage an outbreak of this size and complexity on their own. I urge the international community to provide this support on the most urgent basis possible," she said,.
The agency convened an expert committee this week to assess the severity of the epidemic.
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 50pc.
The impact of the WHO declaration is unclear as a similar announcement made about polio does not yet seem to have slowed the spread of virus.
During a WHO meeting last week to reconsider the status of polio, experts noted that countries had not yet fully applied the recommendations made in May, there have been more instances of international spread, and outbreaks have worsened in Pakistan and Cameroon.
In the United States, the Centres for Disease Control and Prevention (CDC) have already elevated its Ebola response to the highest level and it has recommended against travelling to West Africa.
Yesterday, CDC director Dr Tom Frieden told a Congressional hearing that the current outbreak is set to sicken more people than all previous outbreaks of the disease combined.
Meanwhile, the Spanish missionary priest who tested positive for the Ebola virus is in a stable condition at a Madrid hospital after being evacuated from Liberia.
Miguel Pajares (75) was helping to treat people infected with Ebola and was one of three who tested positive at the San Jose de Monrovia Hospital in Liberia earlier this week.
Juliana Bohi, an Equatorial Guinean nun with Spanish nationality who worked with him, was also brought back but she is not infected.
Both worked for the San Juan de Dios hospital order, a Catholic humanitarian group that runs hospitals around the world.
Mr Pajares and Ms Bohi are being kept in isolation at the Carlos III centre in Madrid, which is run by La Paz hospital.
They arrived at a military air base near Madrid and were strapped to stretchers enclosed by transparent capsule-like tents that were pushed by personnel in protective white suits wearing masks.
Senior regional health official Antonio Alemany said Mr Pajares did not have a fever and the prognosis was good.