The first person to develop Ebola in the United States was struggling to survive at a Dallas hospital yesterday after his condition worsened to critical, the director of the US Centres for Disease Control said.

Thomas Eric Duncan became ill after arriving in Dallas from Liberia two weeks ago – heightening concerns that the worst Ebola epidemic could spread from West Africa, where it began in March and killed more than 3,400 people.

“The man in Dallas, who is fighting for his life, is the only patient to develop Ebola in the United States,” CDC director Dr Thomas Frieden said on CNN’s State of the Union.

Duncan’s case has highlighted problems that American public health officials are trying furiously to address: The Dallas hospital that admitted him initially did not recognise the deadly disease and sent him home, only for him to return two days later in an ambulance.

“The issue of the missed diagnosis initially is concerning,” Frieden said, adding that public health officials had redoubled their efforts to raise awareness of the disease.

“We’re seeing more people calling us, considering the possibility of Ebola – that’s what we want to see,” he said on CNN. “We don’t want people not to be diagnosed.”

Frieden said he was confident the disease would not spread widely within the US. US officials are also scaling up their response in West Africa, where Ebola presents an enormous challenge, he added.

“But it’s going to take time,” Frieden said. “The virus is spreading so fast that it’s hard to keep up.”

In Dallas, a spokesman for Texas Health Presbyterian Hospital, Wendell Watson, said Duncan remained critical yesterday. He would not elaborate.

In Nebraska, another hospital was preparing for the arrival of an Ebola patient who contracted the disease in Liberia, a spokesman said yesterday. Nebraska Medical Center spokesman Taylor Wilson would only identify the patient as a male US citizen expected to arrive today.

Fox TV in Boston identified the Nebraska patient as Ashoka Mukpo, a freelance NBC cameraman working for NBC who contracted Ebola in Liberia. It said he was expected back in the US later yesterday or early today.

The Nebraska hospital last month also treated and released Dr Rick Sacra, an American missionary who also contracted Ebola in Liberia.

Sacra was admitted to a Massachusetts hospital on Saturday for a likely respiratory infection that is not believed to be a recurrence of the disease, hospital officials there said.

The CDC has identified 10 people who had direct contact with Duncan as being at greatest risk of infection. Another 40 were being monitored as potential contacts, out of a group of 114 people initially evaluated for exposure risks, though none from either group has shown symptoms, Frieden said.

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