A top U.S. public health official says the Liberian Ebola patient in the southwestern state of Texas is "fighting for his life" at a Dallas hospital.
Dr. Thomas Frieden of the Centers for Disease Control (CDC) told CNN's State of the Union program Sunday that finding everyone who had contact with Thomas Eric Duncan will help stop Ebola in its tracks.
He said that is why he is confident there will not be an outbreak in the United States. But he said U.S. authorities are deeply concerned about what is happening in West Africa, where he says the longer the epidemic lasts, the more it might spread to other countries.
Duncan's condition worsened Saturday from serious to critical. He was diagnosed with Ebola four days after arriving in the United States September 20 from Liberia.
Frieden said hospitals nationwide have become more vigilant in checking incoming patients for potential risks, particularly among those traveling recently from West Africa.
The CDC has narrowed the number of individuals in Dallas at greatest risk of infection from Duncan, identifying nine people who had direct contact with him.
Another 40 were being monitored as potential contacts, out of a group of 114 people initially evaluated for exposure risks, though none from either group has shown symptoms, Frieden said.
One of the Americans infected while working in the region, Dr. Richard Sacra, was in isolation in Worcester, Massachusetts, after being admitted Saturday for what appeared to be a respiratory infection.
Sacra was treated successfully for Ebola in Nebraska and discharged on September 25. He was stable and being watched for signs of a relapse of the disease at University of Massachusetts Memorial Medical Center, the Boston Globe.
Ebola, which can cause fever, vomiting and diarrhea, spreads through contact with bodily fluids such as blood or saliva.
A hospital patient in Sarasota, Florida, was being monitored and treated for possible symptoms in isolation as a precaution because he, too, had traveled recently to West Africa, Governor Rick Scott said on Saturday.
But a patient admitted under similar circumstances to Howard University Hospital in Washington, D.C., after a recent trip to Nigeria was ruled out as an Ebola victim earlier in the day.
Ebola has killed about 3,500 people in West Africa since the outbreak began last year. Guinea, Liberia and Sierra Leone are the hardest-hit countries.