The lone U.S. Ebola patient is in critical condition, the Dallas hospital that has been treating him reported Saturday.

Texas Health Presbyterian Hospital in Dallas didn't provide any further details about Thomas Eric Duncan's condition and a hospital spokeswoman, Candace White, didn't immediately respond to emails and phone calls. The hospital previously said Duncan was being kept in isolation and that his condition was serious but stable.

Duncan travelled from disease-ravaged Liberia to Dallas last month before he began showing symptoms of the disease.

Health officials said Saturday that they are monitoring about 50 people for signs of the deadly disease who may have had contact with Duncan, including nine who are believed to be at a higher risk. Thus far none have shown symptoms. Among those being monitored are people who rode in the ambulance that transported Duncan back to the hospital before his diagnosis, said Dr. Tom Frieden, the director of the Centers for Disease Control and Prevention.

ADDITION Ebola

Dallas County Judge Clay Jenkins, left, leads a young man from a Dallas apartment where Thomas Eric Duncan, the Ebola patient who travelled from Liberia, stayed last week. (LM Otero/Associated Press)

The items removed by a decontamination crew from the Dallas apartment where Duncan was staying have been hauled away for disposal.

Dallas city spokeswoman Sana Syed said that about 30 barrels were filled Friday with items including bed sheets, towels and three mattresses used by Duncan before he was hospitalized. They were hauled away Friday night.

She said that next, everything else in the house will be disposed of.

The family who lived there was moved to a private home in a gated community, where they are being carefully monitored. The city had been having trouble finding a place that would take in Louise Troh, originally from Liberia, her 13-year-old son and two nephews.

Elsewhere, NBC News reported that an American freelance cameraman working for the network in Liberia has tested positive for the virus and will be flown back to the United States, along with the rest of the news crew.

In Massachusetts, Dr. Richard Sacra, a U.S. doctor and missionary who was successfully treated for Ebola in an Oklahoma hospital and released on Sept. 25, has been readmitted to hospital with what appears to be a respiratory infection. 

"We are isolating Dr. Sacra to be cautious pending final confirmation of his illness," said Dr. Robert Finberg, who is heading Sacra's medical team at UMass Memorial Medical Centre. "We think it is highly unlikely that he has Ebola. We suspect he has an upper respiratory tract infection."

Finberg said the hospital expects conclusive results on Sacra's condition by Monday. 

U.S. officials: We can keep it in check

The first Ebola diagnosis in the U.S. has raised concerns about whether the disease that has killed 3,400 people in West Africa could spread in the U.S. Federal health officials say they are confident they can keep it in check.

The virus that causes Ebola is not airborne and can only be spread through direct contact with the bodily fluids — blood, sweat, vomit, feces, urine, saliva or semen — of an infected person who is showing symptoms.

Ebola

Thomas Eric Duncan, photographed in 2001 at a wedding in Ghana, became the first patient diagnosed in the U.S with Ebola. He has been kept in isolation at a Dallas hospital since Sept. 28. (Wilmot Chayee/Associated Press)

Health officials reported fielding scores of possible cases around the country that have proved to be false alarms. Authorities have responded to inquiries regarding more than 100 potential cases of Ebola since Duncan tested positive, but no new infections have been identified.

Howard University Hospital said on Saturday that a medical team has determined that a patient feared afflicted with Ebola does not have the disease.

Duncan's diagnosis "has really increased attention to what health workers need to do to be alert and make sure a travel history is taken," Frieden told a news conference.

Frieden added that many of the inquiries fielded by the CDC involved people who had travelled outside West Africa.

Duncan arrived in Dallas on Sept. 20 and fell ill a few days later. After an initial visit to the emergency room at Texas Health Presbyterian Hospital, he was sent home, even though he told a nurse he had been in disease-ravaged West Africa. He returned to the hospital two days later, last Sunday, and has been kept in isolation ever since.

The hospital issued a news release late Friday saying that the doctor who initially treated Duncan did have access to his travel history, after all. It had said Thursday that a flaw in the electronic health records systems led to separate physician and nursing workflows, and that the doctor hadn't had access to Duncan's travel history.

With files from Reuters and CBC News