DALLAS (AP) -- The first Ebola patient diagnosed in the United States died Wednesday morning in a Dallas hospital, according to a hospital spokesman. Thomas Eric Duncan was pronounced dead at 7:51 a.m. at Texas Health Presbyterian Hospital Dallas, where he was admitted Sept. 28 and had been kept in isolation, according to spokesman Wendell Watson. "Mr. Duncan succumbed to an insidious disease," Watson said in a statement. Duncan carried the deadly virus with him from his home in Liberia, though he showed no symptoms when he left for the United States. He arrived in Dallas Sept. 20 and fell ill several days later. His condition was downgraded during the weekend from serious to critical. Others in Dallas still are being monitored as health officials try to contain the virus that has ravaged West Africa, with more than 3,400 people reported dead. They also are trying to tamp down anxiety among residents frightened of contracting Ebola, though the disease can be spread only through direct contact with the bodily fluids of an already sick person.