The Liberia national who was the first person diagnosed with Ebola Virus Disease in the United States, Thomas Duncan, has died at a Dallas hospital in Texas.

The hospital’s spokesman, Wendell Watson, said Duncan died on Wednesday morning.

“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,” Watson said in an emailed statement.

Duncan became ill after arriving in Dallas, Texas from Liberia on September 20 to visit family, increasing concerns that the world’s worst Ebola outbreak in history could spread beyond the three worst-hit West African countries.

So far about 48 people whom the Ebola victim had been in contact are being closely monitored.

The Ebola virus has claimed the lives of more than 3,400 people in Liberia, Sierra Leone and Guinea since the outbreak started in March this year.

Duncan was able to gain access to the United States from Liberia’s capital Monrovia, which is one of the worse hit countries; because he did not develop fever when screened at the airport and filled out a questionnaire saying he had not been in contact with anyone infected with the virus.

Liberian officials however said that he lied on the questionnaire, saying that he had been in contact with a pregnant woman who later died of the dreaded disease.

U.S Center for Disease Control and Prevention Director, Thomas Frieden, said he was confident the disease would not spread within the United States, as he noted that U.S. officials are also expanding their response in West Africa.