MONROVIA (AFP) - Liberia's president on Sunday made an impassioned plea for all nations to commit to the fight against Ebola as Madrid announced that a Spanish nurse, the first to be infected outside Africa, had beaten the deadly disease.

Nobel laureate Ellen Johnson Sirleaf said a generation of Africans were at risk of "being lost to economic catastrophe" because of the crisis, warning that the "time for talking or theorising is over".

"This fight requires a commitment from every nation that has the capacity to help - whether that is with emergency funds, medical supplies or clinical expertise," she said in an open letter to the world published by the BBC Sunday.

The worst-ever outbreak of the deadly virus has killed more than 4,500 people, almost all in west Africa, with close to 2,500 deaths registered in worst-hit Liberia.

In Spain, the government said that nurse Teresa Romero, who was hospitalised in Madrid on October 6, had tested negative for the virus.

She will be given another test "in the coming hours", according to a statement from Spain's special Ebola committee, which added that her "health was... developing favourably".

Romero was infected after caring for two Ebola patients who died at Madrid's Carlos III hospital, in the first known case of transmission outside Africa.

Fifteen people who had contact with Romero before she was diagnosed with Ebola, including her husband, are still under observation in hospital.

Isolated cases among health workers in the US and Europe have sparked fear that the epidemic could turn global and prompted Western countries to ramp up their response.

China said on Sunday that it was "very concerned about the seriousness" of the crisis, and pledged to start joint research with France to combat the epidemic.

The deadly virus, for which there is currently no licensed treatment or vaccine, spreads via contact with bodily fluids.

Some countries have managed to get a handle on the outbreak, with Africa's most populous nation Nigeria expected to be declared free of the deadly virus on Monday after 42 days without registering any new infections.

Also on Monday, European Union foreign ministers will meet to devise a new strategy to combat the outbreak, including by freeing up more funds and sending skilled staff to Africa.

"There is a very strong political focus on this as the most immediate crisis facing us," a European diplomat said ahead of the Luxembourg talks.

Another EU diplomat said Britain - which already has a navy ship bound for Sierra Leone laden with medical staff and supplies - hoped to "galvanise EU action on Ebola".

"There is a real sense that this is a tipping point and we must get to grips with it now," said the diplomat. "If we can deal with it in the country, we don't have to deal with it at home." One diplomat said there are plans for three nations to spearhead global aid to the worst-hit countries: the United States for Liberia, Britain for Sierra Leone and France for Guinea.

A global UN appeal for nearly US$1 billion (S$1.27) has so far fallen short, with only US$385.9 million given by governments and agencies, with a further US$225.8 million promised.

With panic spreading in Western countries about the tropical disease, US President Barack Obama on Saturday cautioned Americans against "hysteria".

US media have been reporting on a string of false alarms among a public spooked by the news that two American nurses at a Texas hospital had contracted the virus after treating a Liberian patient who died from Ebola on October 8.

The Texas Health Presbyterian Hospital on Sunday apologised over its handling of the case.

"As an institution, we made mistakes in handling this very difficult challenge," the hospital said in a "letter to our community" that was published in Sunday's Dallas Morning News.

The United States, Britain and Canada were joined by France this weekend in screening air passengers from Ebola-hit zones ahead of a review of EU practices this week.

Belgium's prime minister said it would start screening passengers from west Africa on Monday, while France dismissed a call by unions representing Air France cabin staff to suspend flights to Guinea.

French Foreign Minister Laurent Fabius, speaking during a visit to Beijing, warned that halting the airline's daily Paris-Conakry flight would encourage riskier forms of travel that could spread the virus even faster.

Obama has also played down the idea of a travel ban on flights from west Africa.

As of October 14, 4,555 people had died from Ebola out of a total of 9,216 cases registered in seven countries, the Geneva-based World Health Organisation said.