Texas health officials have expanded to 100 their list of people who may have had contact with a man in the Dallas area confirmed to be infected with the Ebola virus. Eighteen people are already under observation.

The contact estimate provided by the Texas Department of State Health Services (DSHS) on Thursday morning is larger than was originally reported, but it is expected to drop once officials determine how many people must be monitored. Health officials said they were initially looking into a "handful" of people who had come into contact with the infected patient, who traveled to the U.S. from the West African nation of Liberia. He has been identified as Thomas Eric Duncan. 

"Out of an abundance of caution, we're starting with this very wide net, including people who have had even brief encounters with the patient or the patient's home," said Carrie Williams, spokeswoman for the Texas Department of State Health Services. "The number will drop as we focus in on those whose contact may represent a potential risk of infection."

On Wednesday, Dallas County health officials announced that they were monitoring between 12 and 18 individuals in the Dallas area who came in contact with Duncan, including five school-age children who were in contact with the patient after he was sent home from Texas Health Presbyterian Hospital of Dallas. The patient, who presented with a fever and abdominal pain, had disclosed to staff that he had traveled from an area affected by the recent outbreak of the Ebola virus, which has killed 3,000 people in West Africa.

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The patient was sent home from his first visit to the hospital on Sept. 26 with a prescription for antibiotics after hospital staff assessed his condition as a “low-grade viral disease.” He returned on Sept. 28 and was admitted to the hospital to be placed in isolation. The Ebola case was confirmed two days later.

Those being observed by health officials also include five individuals in the "immediate household" where Duncan was staying while visiting from Liberia. This morning, the state health department announced that it was implementing a "strict public health control order" on four close family members who have been instructed to stay in their home and not have any visitors.

“We have tried and true protocols to protect the public and stop the spread of this disease,” said David Lakey, the DSHS commissioner. “This order gives us the ability to monitor the situation in the most meticulous way.”   

The state order requires the family to provide blood samples and "agree to any testing" requested by public health officials. Family members are also required to report any symptoms to Dallas County Health and Human Services, which is monitoring the individuals.

Officials have reiterated that the individuals who are being monitored are not showing any symptoms. Ebola is not easily spread because it can only be transmitted through direct exposure to the bodily fluids — including blood, sweat, saliva, vomit and diarrhea — of someone who is carrying the virus and is showing symptoms.