Two days after he was sent home from a Dallas hospital, the man who is the first person to be diagnosed with Ebola in the United States was seen vomiting on the ground outside an apartment complex as he was bundled into an ambulance.

The Dallas Ebola case, involving a man who flew back to the United States last month from Liberia, has prompted national concern over the potential for a wider spread of the deadly virus from West Africa, where at least 3,338 people have died in the worst outbreak on record.

US health officials have said the country's healthcare system is well prepared to contain any spread of Ebola through careful tracking of people who had contact with the patient and appropriate care for those admitted to hospital.