Natalie DiBlasio

USA TODAY

The first priority of federal health officials is to protect Americans from Ebola, but "an outbreak anywhere is potentially a threat everywhere," the head of the Centers for Disease Control and Prevention said Sunday.

In recent days, a handful of lawmakers, including Louisiana Gov. Bobby Jindal, have called for restrictions on air travel between Ebola-affected countries in West Africa and the United States.

On Saturday, there was a brief scare at Newark Liberty International Airport when a passenger who had traveled from West Africa was ill on a flight from Brussels. A CDC official met the aircraft and the passenger was taken to a hospital, where "it became clear that the symptoms that individual had weren't consistent with Ebola,'' CDC Director Thomas Frieden said. The patient was discharged and was feeling better.

Despite the concerns sparked by such incidents, Frieden emphasized the importance of keeping the travel pipeline open to Ebola-stricken countries in order to fight the outbreak at its source.

"If we don't control the outbreak, there's a real risk that it could spread to other countries in Africa'' and beyond, Frieden said. "To do that, we need regular travel.''

"If we make it harder to fight Ebola in West Africa, we actually increase our own risk," he said. He noted that everyone leaving Guinea, Liberia and Sierra Leone is being screened and said the CDC is considering a plan to screen everyone coming into the U.S. from those countries.

"We've seen a lot of understandable concern because of the deadly nature of Ebola," Frieden said. "We want (people) to be scared. We want them to have a healthy respect."

Before Thomas Eric Duncan was diagnosed in Dallas, the CDC was getting 50 to 100 calls or e-mails daily. Now it's getting about 800.

Health officials traced Duncan's contacts since he arrived in Dallas and found no one exhibiting any symptoms, said David Lakey, Texas health commissioner.

"We are very happy about that, but very cautious," Lakey said. "We are on high alert right now."

Duncan was in critical condition in the intensive care unit in Texas Health Presbyterian Hospital. Frieden said he had taken "a turn for the worse."

In August, two Americans who had contracted Ebola while working in Africa recovered in the United States after receiving the experimental drug ZMapp. Duncan is not receiving the drug because there is none left.

"It takes a long time to make that medicine," Frieden said, "so it's not going to be available any time soon."