Health officials say up to 18 people may have been exposed to the Ebola virus carried by the first known patient diagnosed in the United States. On Wednesday, Texas Gov. Rick Perry said five children have been identified and are being monitored.

Gov. Rick Perry: “Today we learned that some school-age children have been identified as having had contact with the patient and are now being monitored at home for any signs of the disease. I know that parents are being extremely concerned about that development, but let me assure, these children have been identified, and they are being monitored, and the disease cannot be transmitted before having any symptoms.”

The patient, identified as Thomas Eric Duncan, apparently contracted the virus in Liberia when he escorted an Ebola victim to the hospital. After arriving in the United States, Duncan first visited a Dallas hospital last week, complaining of health issues. But he was sent home despite informing staff he was recently in Liberia.