NEW YORK - Some 100 people are now being screened for potential exposure to Ebola in the US State of Texas, federal health officials said Thursday, as they seek to contain the first case of the disease diagnosed in the US, according to American media reports. 

Tom Frieden, director for the Centers for Disease Control and Prevention, said so far they have identified "a handful" of individuals who may have come into contact with the patient, including members of his household.  "We remain confident that we can contain any spread of Ebola," he said.  Texas health officials cautioned that the figure represented a "very wide net," including "people who have had even brief encounters with the patient or the patient's home" and was likely to drop as they narrowed the list to those actually at potential risk of infection, Carrie Williams, a spokeswoman with the Texas Department of State Health Services, said.

So far, the list of people potentially exposed to the disease has been rapidly growing. Earlier Thursday, Dallas County Health and Human Services had put it at around 80, up from less than 20 the day before. The expansion comes as officials try to assess how far exposure to the disease may have rippled since a Liberian man, Thomas Eric Duncan, was diagnosed with the disease on Tuesday.

The list represents everyone who health authorities believe had any contact with the patient; however fleeting or brief, as well as individuals who subsequently had contact with those people, said Erikka Neroes, a spokeswoman for Dallas County Health and Human Services. Once health workers interview those people, they will winnow down the list to a number—likely to be much smaller—of those who they believe may have been exposed to Ebola.

People on the list are being notified by authorities and educated on the signs of Ebola. If they develop any symptoms, they have been told to seek medical treatment and report to health officials.  "Everyone is on the lookout," said Ms. Neroes. "We're just making sure that we keep tracking this again and again until we put this thing to rest."  The 12 to 18 people originally identified by health officials are being monitored by health-care workers, with their temperature being taken twice a day. Among those who had contact with Duncan, authorities previously said, are five children, ranging from elementary to high-school age, as well as a small group of adults. Duncan currently is in an isolation unit at Texas Health Presbyterian Hospital in Dallas. Hospital officials said Thursday that Mr. Duncan's condition continues to be serious. Most of the people on the list haven't been ordered to stay home. However, health officials have formally ordered four of Mr. Duncan's close family members to stay home and not receive any visitors until at least October 19. The family members could face criminal charges if they don't abide by the order. Officials said they issued the order late Wednesday as a precaution, adding that those people haven't developed any symptoms. They had been previously asked to stay home. "This order gives us the ability to monitor the situation in the most meticulous way," said David Lakey, Texas Health Commissioner, in a statement. To date, no one else has been diagnosed with Ebola in Texas. But Ms. Neroes said local health officials are preparing for the possibility that another person might come down with the illness. "There are no other confirmed cases, but there could be," she said.