Authorities in Mali strove to calm fears over Ebola after the disease claimed its first victim in the African country.
The World Health Organization warned the situation in Mali was an "emergency," and said in its latest Ebola situation report that the biggest outbreak on record has now killed 4,922 people, the vast majority of them in Guinea, Liberia and Sierra Leone, with 10,141 cases reported.
The US states of New York and New Jersey ordered mandatory quarantine for medics who had treated victims of the disease in west Africa, after a doctor who had returned from the region became the first Ebola case in New York City.
President Barack Obama sought to calm a jittery public by hugging one of the two nurses who became the first to contract Ebola on American soil after treating a patient, but has now been declared free of the disease.
Mali President Ibrahim Boubacar Keita aimed to ease fears after the death of a two-year-old girl, the first Ebola case in the landlocked country, who travelled from neighbouring Guinea.
"We are doing everything to prevent panic and psychosis," he said in an interview with French radio.
"Since the start of this epidemic, we in Mali took all measures to be safe, but we never hermetically sealed ourselves from this," he said.
"Guinea is a neighbouring country, we have a common border that we have not closed and that we will not close."
- Mali 'emergency' -
But WHO said it was treating the situation in Mali as an "emergency" because the toddler had travelled for hundreds of kilometres on public transport with her grandmother while showing symptoms of the disease -- meaning that she was contagious.
She was said to be secreting bodily fluids -- contact with which is how the virus is passed on.
"The child's symptomatic state during the bus journey is especially concerning, as it presented multiple opportunities for exposures -? including high-risk exposures -- involving many people," the UN agency said.
The girl and her grandmother travelled by public transport from Keweni in Guinea through the towns of Kankan, Sigouri and Kouremale to the Malian capital, Bamako.
"The two stayed in Bamako for two hours before travelling on to Kayes," in Mali's southwest, where treatment was sought for the child, the WHO said.
The route made for a journey of around 1,000 kilometres (620 miles) that would likely take the better part of 24 hours.
"Bleeding from the nose began while both were still in Guinea, meaning that the child was symptomatic during their travels through Mali... multiple opportunities for exposure occurred when the child was visibly symptomatic."
An Ebola victim is contagious when showing symptoms of the virus, such as a high fever.
The Malian authorities were tracing everyone who had contact with the girl and her grandmother and 43 people had been placed under observation, the WHO said.
- Mandatory US quarantines -
New York City's first Ebola case, 33-year-old doctor Craig Spencer who fell ill one week after returning from treating patients in Guinea, was said to be in a stable condition in isolation at the city's Bellevue Hospital Center.
His fiancee and two of his friends are in quarantine but appear healthy, officials said.
In the wake of his diagnosis in the country's largest city, the US states of New York and New Jersey ordered mandatory quarantines of 21 days -- the maximum gestation period for Ebola -- for any individuals who have had direct contact with an Ebola patient while in the worst affected countries.
Dallas-based nurse Nina Pham, who became the first person to contract Ebola in the US after treating an Ebola patient who eventually died at a Dallas hospital, was declared free of the disease.
"I am on my way back to recovery even as I reflect on how many others have not been so fortunate," Pham said before meeting Obama, who gave her a bear hug in an effort to reassure a public nervous over the virus.
Her nursing colleague Amber Vinson, who had also caught the disease, has also been given the all-clear.
- Vaccine doses by 2015 -
The search for an effective vaccine to fight the disease for which there is currently no licensed cure took on fresh urgency as the WHO said several hundred thousand doses could be available in the "first half" of 2015.
Experts are pinning their hopes on the experimental vaccine rVSV, with doses arriving in Geneva for a new round of trials, and ChAd3, made by Britain's GlaxoSmithKline.
Five other potential vaccines are in the pipeline.
Whichever proves effective in trials, WHO hopes to send huge numbers of doses to Africa for "real-world" tests.
"The pharmaceutical companies developing all these vaccines are committing to ramping up the production capacity to millions of doses to be available in 2015," said WHO assistant director general Marie-Paule Kieny.