The first person to be diagnosed with Ebola in the United States died Wednesday morning in a Dallas hospital.

Thomas Eric Duncan, 42, was admitted to the Texas Health Presbyterian Hospital Dallas on Sept. 28. Since then, he has been kept in isolation, said spokesman Wendell Watson. However, his condition worsened from serious to critical on Saturday.

"It is with profound sadness and heartfelt disappointment that we must inform you of the death of Thomas Eric Duncan this morning at 7:51 am. Mr. Duncan succumbed to an insidious disease, Ebola," read a statement released by the Texas Health Resources, according to CNBC.

"He fought courageously in this battle. Our professionals, the doctors and nurses in the unit, as well as the entire Texas Health Presbyterian Hospital Dallas community, are also grieving his passing. We have offered the family our support and condolences at this difficult time," it continued.

Duncan contracted the deadly virus while he was in his home in Liberia and helped carry a sick woman to a hospital. However, he didn't show any signs of the disease when he left for the United States on Sept. 19 and arrived in Dallas on Sept. 20.

A few days a later, he went to the hospital after he began to feel ill on Sept. 25. Although he told hospital workers that he recently traveled from Liberia, where the disease is running rampant, he was sent home. It wasn't until he returned to the hospital on Sept. 28 via ambulance that he was finally tested and diagnosed with the disease.

Medical workers treated the Liberian man with an experimental antiviral drug called brincidofovir, which has been approved by the Food and Drug Administration on an emergency basis.

Texas government officials say they are working to prevent the spread of the disease in Dallas by monitoring 48 people in the area, although no one has shown any symptoms of Ebola, reports the New York Times.

Ten of the people being observed are considered high risk, including the seven health care workers, relatives and community members that had contact with Duncan. The other 38 are considered to be low risk cases, said officials.