HOUSTON - The first group of people monitored for Ebola in the United States will clear the three-week observation period midnight Sunday, with none exhibiting symptoms, as the federal authorities and Pentagon are ratcheting up responses to fight the deadly disease.

More than 200 people in the country are on the watch list for potentially coming into contact with three confirmed Ebola patients, namely a Liberian visitor and two nurses who treated him.

The Liberian man, Thomas Eric Duncan, was the one who brought the virus to the US from West Africa. He arrived in Dallas on Sept 20, fell ill several days later and began showing Ebola symptoms on Sept 24. He went to hospital the second day but was neglected even though he reported his travel history. Duncan was sent to the same hospital on Sept 28 and never walked out of it.

Duncan's diagnosis was confirmed on Sept 30 and he became the first Ebola patient diagnosed on US soil. He died on Oct. 8.

WATCH LIST SHRINKS

Health authorities have identified 48 people in Dallas who had contact, direct or indirect, with Duncan between Sept 24 and Sept 28.

The list includes four family members of Duncan, several emergency crews who rushed him to the hospital, among others. They are deemed to be high risk as they had close contact with Duncan. Others on the list are those who had contact with them in turn.

The 48 people, who have been placed under daily check, will have their 21-day quarantine closed midnight Sunday, with no one showing any signs or symptoms during the Ebola's incubation period.

Duncan's family said in a statement on Sunday, "we are so happy this is coming to an end, and we are so grateful that none of us has shown any sign of illness."

Dallas authorities are expected to officially declare the 48 people clear of Ebola on Monday, marking a watershed in the city's efforts to contain the spread of the disease, though two nurses who cared for Duncan have fallen victim to the virus.

The two nurses are among 77 medical staffers at Texas Health Presbyterian hospital in Dallas who were involved in treating Duncan. Other 75 people have been monitored for Ebola after the two nurses tested positive for the virus. None of them has shown signs of symptoms so far.

Though it is still unclear how exactly the two female nurses, Nina Pham and Amber Joy Vinson, contracted the virus, they are believed to get infected during the first 48 hours, the span of time between Duncan's admittance into the hospital on Sept 28 and his confirmed diagnosed on Sept 30.

Several people who possibly had contact with the two nurses are on the watch list. More than 100 others, who shared a flight with Vinson from Ohio to Dallas on Monday, are also being monitored though experts say their likelihood of being infected is very low.

Vinson was having a slight fever - an early sign of Ebola - before boarding the Frontier flight, and she reportedly asked permission from the US Centers for Disease Control and Prevention (CDC). This has put the CDC under fire, prompting a national outcry and sending fears across the state border of Texas.

The Ebola scare has locked a hospital worker inside a cruise cabin offshore for days. The worker, who did not have contact with Duncan but with his blood sample, incited panic on the cruise ship travelling on the Caribbean sea. It was denied docking by Belize and Mexico along its way.

The ship finally returned to a port in south Texas Sunday - a day after a helicopter landed on it to pick up a blood sample from the worker. News from the CDC came that the worker tested negative for Ebola and that she will be cleared of the disease also on Monday.