The first person to be diagnosed with Ebola within the US has deteriorated from a serious to a critical condition, doctors in the state of Texas say.
Thomas Duncan, who caught the virus in his native Liberia, is being treated at a Dallas hospital in isolation.
Earlier it emerged that the flat where he lived is being cleaned by hazardous materials specialists and its remaining four occupants moved to a private home, the BBC reported.
Some 3,431 people have died in West Africa in the worst Ebola outbreak yet.
A senior US military figure said the US could deploy as many as 4,000 troops to the region to help contain the outbreak, which has hit hardest in West African four nations.
While Mr Duncan is the first person to be diagnosed within the US, three American aid workers and a photojournalist contracted the virus in Liberia.
Texas Health Presbyterian Hospital issued a six-word statement about Thomas Duncan on Saturday, saying only that "Mr Duncan is in critical condition."
Earlier his condition had been described as serious but stable.
A second person in the US has also been admitted to hospital suspected of having the virus.
The patient, who recently travelled to Nigeria, is said to be in a stable condition in a Washington hospital.