As though to illustrate his point, a Dallas bus and train station was closed on Saturday afternoon over concern about a woman who fell ill. The woman was first reported to be on the checklist for possible Ebola exposure but turned out not to be.
While Obama administration and world health officials were still focused on tackling Ebola at its source in three West African countries, Texas state authorities said 14 people had been cleared from an Ebola watch list. On Sunday and Monday, more were expected to end 21 days of monitoring for fever and other symptoms if they are asymptomatic.
They could include Louise Troh in Dallas, fiancee of the now deceased Liberian man who was the first person diagnosed with Ebola in the United States in late September while visiting her. Troh, her 13-year-old son, and two relatives of Duncan have been in mandatory quarantine at an undisclosed location in Dallas.
In all, 145 people with "contacts and possible contacts" with the virus were being monitored, the Texas Department of State Health Services said in a statement.
In his weekly radio address, Obama made plain he is not planning to give in to demands from some lawmakers for a ban on travelers from Liberia, Sierra Leone and Guinea, the worst-hit countries where more than 4,500 people have died since March in the worst Ebola outbreak on record.
"We can't just cut ourselves off from West Africa," Obama said. "Trying to seal off an entire region of the world, if that were even possible, could actually make the situation worse," he said.
Obama has been criticized over his administration's handling of Ebola. He held a flurry of meetings in the past week and on Friday appointed Ron Klain, a lawyer with long Washington experience, to oversee the effort to contain the disease.
Republicans questioned why he did not pick a medical expert.
"I hope he (Klain) is successful in this. I think it's a step in the right direction, but I just question picking someone without any background in public health," Republican Representative Ed Royce, chairman of the House Foreign Affairs Committee, told CNN on Saturday.
The Obama administration is not alone in facing criticism. The World Health Organization has been faulted for failing to do enough to halt the spread of the virus.
The agency promised it would publish a full review of its handling of the crisis once the outbreak was under control, in response to a leaked document that appeared to acknowledge that it had failed to do enough.
There is no cure or approved vaccine yet for Ebola but pharmaceutical companies have been working on experimental drugs. The virus is transmitted through an infected person's bodily fluids and is not airborne.
Canada said on Saturday it would ship 800 vials of its experimental Ebola vaccine, undergoing clinical trials, to the WHO in Geneva, starting on Monday. Iowa-based NewLink Genetics Corp holds the commercial license for the Canadian vaccine.
Britain's biggest drugmaker GlaxoSmithKline said on Saturday that work to develop a vaccine was moving at an "unprecedented rate" and the next phase, if successful, involving vaccinating frontline healthcare workers, would begin early in 2015.
Obama sought to put the extent of the disease in the United States in perspective. "What we're seeing now is not an 'outbreak' or an 'epidemic' of Ebola in America," he said. "This is a serious disease, but we can't give in to hysteria or fear."
A series of Ebola scares has hit the country since the Liberian man, Thomas Eric Duncan, was diagnosed. He died in a Dallas hospital isolation ward on Oct. 8. Americans' faith in the medical system and in authorities' ability to prevent the disease from spreading was jolted by a series of missteps when he was initially not diagnosed.
Two nurses who were part of the team caring for Duncan contracted Ebola. Amber Vinson is being cared for at Atlanta's Emory University Hospital, while Nina Pham is being treated at the National Institutes of Health just outside Washington.
A chain of people who had contact with either Duncan or the sick nurses are being monitored. Some 800 passengers who took the same planes as Vinson on a trip she made to Ohio before being diagnosed, and passengers on subsequent flights using the same planes, have been contacted by the airline, Frontier Airlines, the carrier said on Saturday.
The airline said in a letter to employees that it had been informed by the U.S. Centers for Disease Control and Prevention that the Dallas nurse may have been in a more advanced stage of the illness than previously thought when she traveled back to Dallas from Cleveland on Oct. 13.
Those being monitored include a lab worker at the hospital, who is not ill but is in isolation at sea in her cabin on the Carnival Magic cruise ship owned by Carnival Corp. The lab worker did not have contact with Duncan but may have come in contact with test samples. The ship was on its way back to Galveston, Texas.
Obama has stressed that containing Ebola should include help for the worst-hit countries and Washington plans to deploy up to 4,000 military personnel to the region by late October. Obama is preparing to ask for additional funds from Congress to beat Ebola and could make the request next week, according to a Bloomberg report.
British Prime Minister David Cameron said on Saturday European Union leaders should raise the amount of money pledged to fight Ebola to 1 billion euros ($1.3 billion) and mobilize at least 2,000 workers to head to West Africa. A spokeswoman at Cameron's office said the EU commission and 28 member states had pledged a total of 500 million euros so far to fight Ebola.
Combating the disease was also among the subjects of talks being held on Friday and Saturday between American and Chinese top diplomats.