(CNN) -- [Breaking news alert published at 5:50 p.m. ET]
A person traveling from Liberia to the United States has been diagnosed with Ebola, Dr. Thomas Frieden, director of the Centers for Disease Control and Prevention, told reporters Tuesday. The person, whose identity was not released, left Liberia on September 19 and arrived in the United States on September 20, he said. At that time, the person did not have symptoms. \"But four or five days later\" that person began to show symptoms, Frieden said. The person was hospitalized and isolated Sunday at a hospital in Texas, he said.
[Original story published at 5:42 p.m. ET]
A patient being treated at a Dallas, Texas, hospital is the first person diagnosed with Ebola in the United States, the Centers for Disease Control and Prevention announced Tuesday.
Several other Americans were diagnosed in West Africa and then brought to the United States for treatment.
The person who first tested positive for Ebola in the United States is a patient at Texas Health Presbyterian Hospital in Dallas, hospital spokesman Stephen O'Brien said Tuesday.
The adult patient developed symptoms days after returning to Texas from West Africa, and was admitted into isolation on Sunday, according to the Texas Department of State Health Services.
The CDC is expected to provide more details on the case in a press conference at 5:30 p.m.
The Ebola outbreak has been centered in the West African countries of Guinea, Sierra Leone and Liberia, though there have been concerns about international air travel and other factors -- including the fact the symptoms might not appear until two to 21 days after one is infected -- may contribute to its spread.
More than 3,000 people in West Africa have died after being infected with Ebola, according to a World Health Organization report from last week. The same report stated that there had been 6,553 cases of the virus overall, though the number is suspected of being much higher given difficulties in tracking and reporting the disease.
According to the CDC, Ebola causes viral hemorrhagic fever, which can affect multiple organ systems in the body and are often accompanied by bleeding. Early symptoms include sudden onset of fever, weakness, muscle pain, headaches and a sore throat, each of which can be easily mistaken early on for other ailments like malaria, typhoid fever, meningitis or even the plague.
CNN's AnneClaire Stapleton contributed to this report.