Fears over the Ebola outbreak are growing after the first patient diagnosed with the disease in the United States is now in critical condition.

Thomas Eric Duncan is being treated at a Dallas hospital. The Liberian man started developing symptoms of Ebola after arriving in Texas on Sept. 20.

CDC Director Tom Frieden says officials are monitoring everyone Duncan has come into contact with.

Meanwhile, Sen. Charles Schumer (D-N.Y.) says federal airport agents should take the temperatures of passengers arriving from West Africa to prevent Ebola from spreading. Schumer is also calling for a database of anyone who recently visited West Africa for hospitals to use.

More than 3,000 people in West Africa have died from the outbreak, according to health officials.