Centers for Disease Control and Prevention (CDC) Director Dr. Thomas Frieden speaks at the CDC headquarters in Atlanta, Georgia in this September 30, 2014 file photo. A health worker in Texas at the hospital where the first person diagnosed with Ebola in the United States died last week has tested positive for the deadly virus in a preliminary test, the state's health department said on October 12, 2014. REUTERS/Tami Chappell/Files (UNITED STATES - Tags: HEALTH)

By Lisa Maria Garza

DALLAS Texas (Reuters) - A Texas health worker has contracted Ebola after treating a Liberian who died of the disease in Dallas last week, raising concern about how U.S. 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. Duncan, a Liberian, was exposed to Ebola in his home country and developed the disease while visiting the United States.

The new case prompted President Barack Obama to order federal authorities to take additional steps to ensure the American medical system is prepared to follow correct protocols in dealing with Ebola, the White House said on Sunday.

There was no word yet how the health worker was infected, but the director of the Centers for Disease Control and Prevention (CDC) said it indicated a professional lapse that may have caused other health workers at the hospital to be infected as well.

"We don't know what occurred in the care of the index patient, the original patient, in Dallas, but at some point there was a breach in protocol, and that breach in protocol resulted in this infection," CDC director Dr. Thomas Frieden told a news conference.

Hospital officials said the worker had been wearing CDC-recommended protective gear during treatment, including gowns, gloves, masks and shields.

"We are evaluating other potential healthcare worker exposures because if this individual was exposed, which they were, it is possible that other individuals were exposed," Frieden said.

Tests by the CDC confirmed the patient had been infected with Ebola.

Frieden said there was one person who may have had contact with the infected health worker when she could transmit the disease and that person is being monitored.

None of the 10 people who had close contact with Duncan or 38 people who had contact with that group have shown any symptoms, state health officials said. The infected worker was not among the 48 being monitored.

In a sign of concern over the spread of Ebola, a patient in Massachusetts who recently returned from Liberia and was displaying symptoms of Ebola was transferred from a medical clinic to a Boston hospital on Sunday, the hospital said.

The patient has not been confirmed to have the virus.

Harvard Vanguard Medical Associates hospital in Braintree, where the patient first went, was closed briefly to deal with the case but reopened, Ben Kruskal, a physician and chief of infectious disease, said in a statement.

In the case of Duncan, the Liberian who died in Dallas, the hospital failed to recognize that he might have Ebola when he first went to the emergency room and he was sent home, admitted and diagnosed two days later when his condition was more serious.

In an effort to stop the spread of the disease, New York's John F. Kennedy Airport on Saturday began the screening of travelers from the three hardest hit West African countries. The airport is the first of five U.S. airports to start enhanced screening of U.S.-bound travelers from Guinea, Liberia and Sierra Leone.

In Liberia, thousands of Liberian healthcare workers are set to begin an indefinite strike at midnight on Monday which could undermine the country's effort to stop the spread of the virus and leave several hundred patients without care.

The Ebola virus causes hemorrhagic fever and is spread through direct contact with body fluids from an infected person, who suffers severe bouts of vomiting and diarrhea.

The Texas case is not the first outside West Africa in which a health worker contracted the disease after contact with a patient.

In Spain, a nurse who contracted Ebola after caring for two infected priests repatriated to Spain remained seriously ill but showed signs of improvement. Teresa Romero, 44, is so far the only person who has tested positive for Ebola through a transmission in the country.

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