: A Texas health care worker has become the first person to contract Ebola on American soil, authorities confirmed Sunday, sparking jitters that safety precautions taken by medical staff could be insufficient.
Top US health officials have said a breach of protocol was to blame for the new Ebola patient -- the second person infected outside Africa and the second diagnosed in the United States.
The news deals a blow to global efforts to stem the epidemic, which has already claimed more than 4,000 lives, most of them in the hard-hit West African countries of Guinea, Liberia and Sierra Leone.
"This development is understandably disturbing news for the patient, the patient's family and colleagues and the greater Dallas community," the US Centers for Disease Control and Prevention said.
But the CDC insisted that any further spread into the community surrounding the Dallas hospital "can be prevented with proper public health measures."
Earlier, the agency's chief Thomas Frieden said it was clear that "at some point there was a breach in protocol and that breach in protocol resulted in this infection."
The CDC has launched a probe, as well as a hunt for more health care workers who may have been exposed to the dangerous virus.
US President Barack Obama said that federal authorities should take "immediate additional steps" to make sure hospitals were ready to follow protocols designed for Ebola patients, according to the White House. 'Breach in protocol'
The unidentified female caregiver at Texas Health Presbyterian Hospital in Dallas tested positive for Ebola on Saturday in a preliminary test and is currently in the hospital, in isolation and in stable condition.
"This is not news that should bring about panic," said Dallas County Judge Clay Jenkins.
But Dan Varga, the chief clinical officer for Texas Health Resources, said the woman "was following full CDC precautions" -- protective gear that would have included a mask, gown and gloves.
Frieden said the woman had "extensive contact" with Thomas Eric Duncan, a Liberian man who was diagnosed with Ebola in the United States last month and died in Texas on Wednesday.
"We are evaluating other potential health care worker exposures," said Frieden. "It is possible that other individuals were exposed."
Duncan was believed to have been infected before he left Liberia and boarded a plane to visit family in Texas.
Meanwhile in Nebraska, a 33-year-old American photojournalist who became infected with Ebola while working in Liberia was continuing to show improvements, doctors said. 'Far ahead of us'
The latest case underlines United Nations fears and growing concerns in the United States about Ebola, for which there is no vaccine or widely available treatment.
"The virus is far ahead of us and every day the situation gets worse," the head of the United Nations' emergency Ebola mission, Anthony Banbury, told UN leaders after a tour of the three hard-hit West African countries.
New York's JFK airport on Saturday became the first in the country to launch health screenings for travelers from epidemic-hit West Africa.
Other nations have instituted similar checks.
Passengers from West Africa arriving at John F Kennedy International Airport in New York and other major US hubs in Atlanta, Chicago, Newark and Washington will have their temperatures taken, be screened for signs of illness and answer questions about possible exposure.
"Exit screening might not find every person with Ebola; however, it does not have to be perfect to help reduce the spread of Ebola," the CDC said in a statement. Nurse's condition improves
In Spain, attention remained focused on 44-year-old Teresa Romero, the Madrid nurse who became the first person infected with the hemorrhagic fever outside of Africa.
The Spanish crisis cell set up after she fell sick said there was "reason to hope" she could recover.
"It seems the viral charge has been brought under control and is diminishing," said Fernando Simon, head of the team set up within the health ministry.
Simon added, however: "We must be highly cautious since this is someone infected with Ebola whose situation remains critical and it is possible that other organs are affected."
Romero is thought to have contracted the disease in late September in a Madrid hospital while caring for a Spanish missionary infected with Ebola in Africa who later died.
Romero has said she thought she might have developed Ebola after brushing her face with a glove -- pointing to possible gaps in the safety protocols in hospitals treating Ebola patients.
Fifteen other people, mostly hospital staff as well as Romero's husband, are under observation at the Carlos III hospital where Romero is being treated. Rising toll
The World Health Organization reported 4,033 people have died from Ebola as of October 8 out of a total of 8,399 registered cases in seven countries.
Ebola causes fever, diarrhea, vomiting and in some cases internal and external bleeding. It is spread by contact with bodily fluids or exposure to contaminated objects such as needles.
The United Nations says aid pledges to fight the epidemic have fallen well short of the $1 billion needed.