The UN has launched a mission to prevent the global spread of Ebola, describing the epidemic as the world’s “highest priority” as the US scrambled to limit its own outbreak to one patient.

Anthony Banbury, head of the UN Mission on Ebola Emergency Response (UNMEER), began a tour of the three hardest-hit nations in the Liberian capital Monrovia, setting out an ambitious goal to eradicate the deadly virus.

“The only way we will end this crisis is if we end every single last case of Ebola so there is no more risk of transmission to anyone, and when that’s accomplished, UNMEER will go home,” he said on Thursday.

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The agency will work on health and education, Banbury said. But it will also make more vehicles available in the response and helping Ebola-free neighbouring countries defend themselves against a possible spread.

“The sooner UNMEER can end, the better for all of us. It’s my hope that it will be as soon as possible because that means fewer lives will be lost,” he told reporters.

President Ellen Johnson Sirleaf had told Banbury on his arrival in Liberia, the worst-hit nation with almost two-thirds of the 3338 deaths in west Africa, that the virus had spread to all 15 of its counties.

US health officials, meanwhile, were scouring the Dallas area for people who came in contact with a Liberian man diagnosed with Ebola.

A Liberian hospital worker watches a burial team remove the bodies of Ebola victims, while sanitised boots and gloves dry in the background. Photo: Getty

The man – the first person to be diagnosed with Ebola on US soil – flew from Liberia and arrived in Texas September 20 to visit family. He fell ill on September 24, reportedly after helping a pregnant woman in Liberia who later died of Ebola. He is in serious but stable condition.

Health officials said they were monitoring 100 people for signs of Ebola and ordered four of the man’s “close family members” to stay at home.

The World Health Organisation said in its latest situation update there was still a “significant shortfall” in capacity in west Africa, with 1500 more beds needed in Liberia and 450 in Sierra Leone.

Around 160 health professionals pledged by Cuba to Sierra Leone arrived on Thursday.

Meanwhile Doctors Without Borders, the global aid agency leading the response in west Africa, with 3000 staff including about 250 Western volunteers, has criticised the inadequacy of international aid, saying it desperately needs medical teams rather than cash.

A charity, Save the Children, warned that five people are being infected with Ebola every hour in Sierra Leone and demand for treatment beds is far outstripping supply.

If the current “terrifying” rate of infection continues, 10 people will be infected every hour with the deadly virus in the country by the end of October, the London-based group warned.

US oil giant ExxonMobil meanwhile said it had limited employee travel to the west African countries hit by Ebola, and delayed the start of an exploration well in Liberia.