Ohio Woman Being Tested for Ebola U.S. doctors on the lookout for possible Ebola cases.

 -- Hospitals across the country are isolating and testing potential Ebola patients, erring on the side of caution as the largest Ebola outbreak to date rages in West Africa.

A 46-year-old Columbus, Ohio, woman who recently traveled to one of the three countries affected by the outbreak is being held in isolation at a local hospital, the Columbus health department said today. She was hospitalized several days ago but is “doing well” as she awaits Ebola test results from the Centers for Disease Control and Prevention, which are expected today or Wednesday, the health department said.

The CDC last week sent a health alert to hospitals across the country urging them to ask patients about their travel history to help identify potential Ebola cases. The CDC said has tested blood samples from six people with possible Ebola symptoms who had recently traveled to West Africa.

Emergency room physicians at Johns Hopkins Medicine thought one of their patients had Ebola Friday, but it turned out to be a false alarm, according to an internal memo obtained by ABC News.

The patient was ultimately diagnosed with malaria, but Dr. Trish Perl, a senior epidemiologist at the hospital in Baltimore, wrote in a memo to her staff that those involved did a "remarkable job" identifying and isolating the patient as well as making sure a minimal number of people were at risk for contracting the virus.

"This is a 'wake up' call for all of us to recognize that we are vulnerable because of the patients we serve and our location," Perl wrote.

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Johns Hopkins Medicine said it could not provide more information because of patient confidentiality and federal privacy laws.

"Our staff trains frequently to ensure that the hospital is prepared for all types of scenarios," the hospital said in a statement to ABC News. "If a patient were to have suspected Ebola virus, the patient would be placed in isolation, staff would begin taking standard precautions, and the patient would be evaluated by our infectious disease specialists."

On Monday, Mount Sinai Hospital in New York City announced that it was treating a potential Ebola patient who recently traveled to West Africa and was experiencing a high fever and gastrointestinal symptoms.

“Many things cause fever and gastrointestinal symptoms,” ABC News chief health and medical editor Dr. Richard Besser said shortly after Mount Sinai’s announcement on Monday. “The steps they are taking are wise given the travel history, but nothing about the symptoms is specific to Ebola.”

Doctors isolated the patient and sent blood samples to the CDC for testing, but Mount Sinai officials said at a news conference Monday night that the patient was "unlikely" to have the deadly virus.

The death toll of the Ebola outbreak in Guinea, Liberia, Nigeria and Sierra Leone climbed to 887, the World Health Organization said Monday. 1,603 people have been infected, in all.

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