Thomas Eric Duncan, the Liberian man who had been diagnosed with Ebola in Dallas, Texas, died on Wednesday. He was 42.

Duncan was the first person to have been diagnosed with the virus in the United States. He had been receiving the experimental drug Brincidofovir since Saturday. Texas Health Presbyterian Hospital, where he was being treated, said Tuesday afternoon that Duncan was on a ventilator and had been receiving dialysis.

Days before his death, his condition was downgraded from serious condition to critical but stable condition.

"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," a hospital spokesperson said. "Mr. Duncan succumbed to an insidious disease, Ebola. 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's not clear exactly when or where Duncan contracted the disease, but in mid-September he had assisted a woman in Liberia who later died of Ebola. Duncan and others had helped bring Marthalene Williams, 19, to the hospital.

Duncan arrived in Dallas on Sept. 20 to visit his partner, Louise Troh. On Sept. 25, after he complained of a fever and abdominal pain, Troh drove him to the Texas hospital, where health care workers sent him home with antibiotics. It was only after his condition worsened days later that he was taken back to the hospital in an ambulance and placed in isolation.

The Texas hospital has been sharply criticized for failing to recognize Duncan's symptoms, even though he told them he had come from Liberia, where the virus has run rampant. Last Thursday, the hospital said that a flaw in their computer system prevented the information from reaching doctors. They walked back that statement on Friday but provided no alternative explanation.

Meanwhile, the Center for Disease Control and Prevention has been monitoring 38 people who may have come into contact with Duncan, including hospital employees and family members. So far, none of them have showed any of the typical Ebola symptoms.

Duncan's family visited him on Monday and was disturbed by his condition.

"What we saw was very painful. It didn't look good," said Josephus Weeks, his nephew.

"The past week has been an enormous test of our health system, but for one family it has been far more personal," said David Lakey, the commissioner of the Texas Department of State Health Services. "Today they lost a dear member of their family. They have our sincere condolences, and we are keeping them in our thoughts. The doctors, nurses and staff at Presbyterian provided excellent and compassionate care, but Ebola is a disease that attacks the body in many ways. We’ll continue every effort to contain the spread of the virus and protect people from this threat."