A Texas health worker has contracted Ebola after treating a Liberian who died of the disease in Dallas, US last week, raising concern about how US medical guidelines aimed at stopping the spread of the disease were breached. Texas Health Presbyterian Hospital in Dallas, where the new case was announced on Sunday, has already faced criticism for its management of the infection.The infected worker, a woman who was not named, is the first person to contract the disease in the United States. She had close and frequent contact during the 11-day treatment of Thomas Eric Duncan, who died on Wednesday, health officials said.The current Ebola outbreak is the worst outbreak on record and has killed more than 4,000 people, mostly in West Africa's Liberia, Sierra Leone and Guinea.