DALLAS — The first Ebola patient diagnosed in the United States died this morning in a 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 has been kept in isolation, according to spokesman Wendell Watson.

Duncan carried the deadly virus with him from his home in Liberia, though he showed no signs when he left for the United States. He arrived in Dallas Sept. 20 and fell sick a few 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.

The hospital has changed its explanation several times about when Duncan arrived and what he said about his travel history. It has acknowledged that Duncan told them on his first visit that he came from West Africa.