MONROVIA : The UN launched a mission on Thursday to prevent the worldwide spread of Ebola as the US hunted for people who came in contact with the first African diagnosed with the deadly virus outside the continent.

Anthony Banbury, the special representative for the UN Mission on Ebola Emergency Response (UNMEER), was expected to set ambitious targets for action on the crisis as he began a tour of the three worst-hit nations in the Liberian capital Monrovia.

President Ellen Johnson Sirleaf said she had told Banbury the virus had spread to all 15 counties of Liberia, the worst-hit nation with almost two-thirds of the 3,338 deaths in west Africa.

“Affected people are leaving from urban places and hiding out in remote communities,” Sirleaf said, according to a statement from the presidency following the meeting on Wednesday.

“If we do not move in as quickly as possible, the virus (will) further spread in rural areas.”

Banbury was due to address the media before moving on to Sierra Leone and then Guinea over the coming days, with US health officials scouring the Dallas area for people who came in contact with a Liberian man diagnosed with Ebola.

The man first sought treatment in Texas on September 25 but hospital officials have admitted he may have come into contact with many more people than first thought because an apparent miscommunication among staff resulted in his release back into the community for several days.

Ebola is spread through close contact with the bodily fluids of an infected person, and can only be transmitted when a patient is showing symptoms like fever, aches, bleeding, vomiting or diarrhoea.

The man - the first person to be diagnosed with Ebola on US soil - flew from Liberia, the hardest-hit nation in west Africa’s deadly Ebola outbreak, and arrived in Texas September 20 to visit family. He fell ill on September 24.

He went to the hospital the next day but was sent home because the medical team “felt clinically it was a low-grade common viral disease”, said Mark Lester, executive vice president of Texas Health Resources.

“He volunteered that he had travelled from Africa in response to the nurse operating the checklist and asking that question,” Lester added.

“Regretfully, that information was not fully communicated throughout the full team.”

The patient is currently in serious but stable condition.

The Liberian government expressed “regret” on Thursday over the spread of Ebola from Monrovia to the US, adding that the incident had demonstrated “the clear international dimension of this Ebola crisis”.

The incubation period for Ebola is between two and 21 days. Patients are not contagious until they start to have symptoms but once the disease takes hold it can lead to massive bleeding and fatal organ failure.

Britain hosted a conference in London on Thursday to gather support for the fight against Ebola in Sierra Leone, its former colony which has seen more than 600 deaths.

President Ernest Bai Koroma had been due to be the guest of honour at the half-day meeting, which has brought together ministers, diplomats and health officials from around 20 countries and world organisations.

But a plane chartered to fly him to London was unable to take off due to “technical difficulties”, the UK Foreign Office said.

Save the Children warned as the conference began 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 West African country by the end of October, the London-based charity warned.

“We need a coordinated international response that ensures treatment centres are built and staffed immediately,” chief executive Justin Forsyth said in a statement.

Britain has pledged £120 million ($190 million, 150 million euros) to help build an estimated 700 treatment beds, fund new community treatment centres, support existing public health services and support aid agencies in Sierra Leone.

Officials are hoping to secure pledges of support and money at Thursday’s meeting, as well as to share best practices with those working in Liberia and Guinea.

The United Nations has announced its first suspected victim of Ebola, a Liberian man who worked for the UN mission in Liberia and died of a probable but unconfirmed infection last week.

In response to the fast-moving outbreak, the World Bank boosted its aid to the campaign by adding $170 million toward expanding the health-care workforce and buying needed supplies for care and treatment.

The new aid took to $400 million the amount the bank has put toward the fight against the spread of Ebola, which has swept quickly through Liberia, Guinea and Sierra Leone.