President Obama discussed the misinformation on Ebola and what the U.S. is doing to combat the deadly virus in his weekly address on Saturday. (Reuters)

President Obama on Saturday sought to tamp down fears of an Ebola outbreak and defend his administration from Republican critics who have called for a more aggressive response to the disease, including sealing off U.S. borders to visitors from countries battling widespread outbreaks.

“We can’t just cut ourselves off from West Africa, where this disease is raging,” Obama said in his weekly radio address. “Trying to seal off an entire region of the world — if that were even possible — could actually make the situation worse.”

Such actions would make it harder for American health-care workers, soldiers and supplies to reach stricken areas and could prompt residents of countries in West Africa where Ebola is still spreading to try to evade screening on their way to the United States or Europe, Obama said.

The president’s main message was one of calm, coming at a time of growing worry in communities throughout the country. “We can’t give in to hysteria or fear, because that only makes it harder to get people the accurate information they need,” Obama said. “If we’re guided by science — the facts, not fear — then I am absolutely confident we can prevent a serious outbreak here in the United States.”

Later on Saturday, Obama received updates on the process to identify and monitor individuals who may have come into contact with Ebola patients in Dallas. The president also was informed about measures to ensure that the city had all the resources it needed to diagnose new cases, the White House said.

This is what a passenger arriving at Dulles can expect if he is coming from one of the countries hard-hit by Ebola:

As Ebola fears have spread, some urgent-care clinics have taken steps to identify red flags, such as recent travel to West Africa, before patients ever set foot in the clinic. AFC/Doctors Express, a national chain of more than 130 urgent-care clinics, with facilities in Alexandria, Va., Woodbridge, Va., Edgewater, Md., and Towson, Md., fields some of its patient calls through a national call center that’s designed to screen symptoms before patients show up to see a doctor. On Friday, the call center developed a new Ebola fact sheet and script to ask patients about their travel history, said Glenn Harnett, the chief medical officer for AFC/Doctors Express.

More Often, the clinics have seen cases of irrational fear. Some patients have requested Ebola tests even though they aren’t ill, Harnett said. He told the story of one patient who had recently traveled to Mobile, Ala., and requested that he be screened for Ebola, despite having no symptoms nor any interaction with someone who was sick. The patient had grown concerned because of Mobile’s position as a port city and felt that he might be vulnerable to exposure.

“We’d probably have lines down the street if we had an Ebola vaccine, but so many more Americans will die of influenza,” Harnett said. “I find that somewhat frustrating as a clinician, but people are people, and they’re going to have the fears that they have.”

Some of those fears have even reached the White House, where a petition calling for the Federal Aviation Administration to ban flights to and from Ebola-stricken regions had more than 45,000 signatures by Saturday evening. In the heat of election season, politicians have begun weighing in on the issue. And citizens have swarmed social media to share stories of local hysteria.At the Pentagon, workers donned hazmat suits to clean up after someone got sick in the bathroom.

In the Washington area, Howard J. Bennett, a pediatrician and author, said he was asked by one concerned patient about the chances of contracting Ebola by using a bathroom at a mall where someone with the disease had visited. Bennett said he reassured the patient that it was safe.

Obama on Saturday stressed that an outbreak of the disease in the United States was, at best, a remote possibility. He noted that Ebola is much harder to contract than the flu and can be spread only through contact with the bodily fluids of someone who is showing symptoms of the disease. He also emphasized that U.S. health-care officials had established protocols to fight the disease and prevent its spread.

In Dallas, two nurses did contract the deadly virus from a Liberian man, Thomas Eric Duncan, who later died of the disease. One of those nurses, Nina Pham, was being treated at the National Institutes of Health outside Washington, where she was in fair condition and “resting comfortably,” a spokesman said.

On Saturday, Duncan was remembered by family and friends at a memorial service in a small Southern Baptist church in Salisbury, N.C.

Spencer Hsu contributed to this report.