The United States has diagnosed its first case of Ebola in a man who was infected in Liberia and travelled to Texas, US health officials said on Tuesday, pledging to contain the virus that has killed more than 3,000.
The man is also the first to be diagnosed outside Africa, the Centers for Disease Control and Prevention said, cautioning that since he was not sick on the plane he was unlikely to have infected other travellers.
CDC chief Tom Frieden vowed that US health authorities would be able to contain the virus and the White House said President Barack Obama had been briefed by the CDC about the Texas case.
"We are stopping this in its tracks," said Frieden, describing the man as critically ill.
The world's largest outbreak of Ebola has infected more than 6,500 people across five west African countries and killed 3,091 since the start of the year, according to the World Health Organization.
The CDC warned last week that a worst-case scenario could see Ebola cases explode to 1.4 million worldwide by January, but that such dire predictions could be avoided if resources are scaled up.
The United States has already treated several patients who acquired Ebola during the West African outbreak, including Christian missionary doctors Kent Brantly and Rick Sacra, who have been declared free of the virus.
Another patient with suspected exposure to Ebola was hospitalised outside the US capital over the weekend, but it remains unclear whether that person has Ebola or not.
There is no vaccine or drug to treat Ebola, which first emerged in Africa in 1976.
- No risk to airline travellers -
Frieden said the Texas patient, whose identity and nationality were not revealed, left Liberia on September 19 and arrived in the United States a day later to visit family in Texas.
He did not begin experiencing symptoms until the 24th. He sought treatment on the 26th and was placed in hospital isolation on the 28th.
Ebola is not contagious until patients show symptoms, which can include fatigue, fever, muscle aches, vomiting, diarrhea and bleeding.
"At this point there is zero risk of transmission on the flight. The illness of Ebola would not have gone on for 10 days before diagnosis," Frieden said.
"He was checked for fever before getting on the flight and there is no reason to think that anyone on the flight that he was on would be at risk."
Ebola is spread by close contact with the bodily fluids of an infected person who is showing symptoms, or by touching the corpse of a person who died from the hemorrhagic virus.
Frieden said a "handful" of people, mainly family members, are believed to have come in contact with the man while he was sick. They are being monitored closely for symptoms.
- Rapid spread -
The beginning of the West Africa outbreak has been identified as a two-year-old boy in Guinea who became sick with Ebola in December 2013.
Experts do not know how the child came down with Ebola, but the New England Journal of Medicine has reported that he may have come in contact with an infected fruit bat, which are natural hosts for the virus.
Since then the disease has spread rapidly, primarily affecting Sierra Leone, Liberia, and Guinea and overwhelming the healthcare systems there.
Ebola spilled into Nigeria in July by a dual US-Liberian citizen who flew on a plane from Liberia to Lagos. The outbreak there killed eight and infected 20 people, the WHO said.
But the Ebola outbreak in Nigeria is almost over, US health officials said separately on Tuesday, in a rare sign of authorities turning the tide on the highly contagious disease.
Any modern American hospital with an intensive care unit should be well equipped enough to isolate a patient with Ebola, and give supportive care.
Some lawmakers have urged the US government to take stronger action to prevent Ebola from entering the country.
"Today's CDC announcement shows the need for active screening for Ebola at US points of entry," said Ohio Senator Rob Portman.
California congressman Ed Royce, who chairs the House Foreign Affairs Committee, said Ebola "presents a clear and present danger not only to West Africa, but to the broader international community."