The first person diagnosed with Ebola in the United States has been identified as Liberian citizen Thomas Eric Duncan. About 100 people are now being monitored for Ebola after they had direct or indirect contact with Duncan.

Duncan, who is in serious condition, is being treated in an isolation unit at Texas Health Presbyterian Hospital in Dallas, where he was brought by ambulance earlier this week.

On Sept. 19, Duncan flew from Liberia to Brussels. From there, he traveled to Washington’s Dulles Airport before flying to the Dallas-Fort Worth Airport on a United Airlines flight. The Centers for Disease Control and Prevention (CDC) said airline passengers and flight crew members are not at risk for Ebola because Duncan did not show symptoms until days after his flight. Ebola is not contagious until symptoms appear, and it can only be spread by direct contact with bodily fluids, such as blood and saliva.

Medical authorities originally said they were interviewing and monitoring 12 to 18 people, including five children, who had been in contact with Duncan since his arrival in the United States. According to a New York Times report, officials said that up to 100 people are now being monitored, including Duncan’s contacts and people with whom they had contact. The five children are being kept home from school and the four schools they attend have been thoroughly sanitized, officials said.

Keep Reading: Why This Ebola Epidemic Won’t Become the ‘Black Death’ of the 21st Century »

Four members of Duncan’s family are under a “control order” to remain inside their homes and to not have visitors until the three-week incubation period for the virus has passed. According to authorities, Duncan’s family members do not have symptoms of Ebola at this time. The control order will stand until at least Oct. 19.

In a statement, Texas health officials said a “strict public health control order is needed to ensure compliance.” Dr. David Lakey, Texas health commissioner, said, “This order gives us the ability to monitor the situation in the most meticulous way.”

At a news conference, Dr. Edward Goodman, an epidemiologist at Texas Health Presbyterian Hospital, said the ambulance workers and other healthcare professionals who treated Duncan are also being monitored.

Meanwhile, Texas Health Presbyterian is under fire for letting Duncan leave the hospital when he first arrived there for care on Sept. 26. He was sent home with an antibiotic, only to come back to the hospital in an ambulance two days later.

Duncan reportedly told a nurse during his first visit that he had traveled from West Africa. Mark Lester, the executive vice president of Texas Health Resources, said in a statement, “Regretfully, that information was not fully communicated throughout the full team.”

According to a CNN report, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said, “A travel history was taken, but it wasn’t communicated to the people who were making the decision. … It was a mistake. They dropped the ball.”

Learn About the Ebola Drug Grown Inside Plants »

Ten experts from the CDC – supported around the clock by the CDC’s Emergency Operations Center and Ebola experts in the CDC’s Atlanta headquarters – have arrived in Texas and are working closely with Texas state and local health departments.

“We are stopping Ebola in its tracks in this country,” said CDC director Dr. Tom Frieden in a press release. “We can do that because of two things: strong infection control that stops the spread of Ebola in healthcare; and strong core public health functions to trace contacts, track contacts, isolate them if they have any symptoms, and stop the chain of transmission. I am certain we will control this.”

The virus is still on the rampage in West Africa, killing an estimated 3,300 people so far. Humanitarian group Save the Children reported today that five people every hour are being infected with Ebola in Sierra Leone, many of them children.

Photo courtesy of fcn80/Flickr.