Heightened concern about the Ebola virus has led to alarms being raised at three hospitals in New York City. But so far, no Ebola cases have turned up.

The latest episode involved a man who had recently been to West Africa, and who went to the emergency room at Mount Sinai Hospital in Manhattan late Sunday with a high fever and gastrointestinal problems, the hospital reported on Monday. He is being kept in isolation at the hospital while tests are being done for Ebola, a deadly disease, but also for other illnesses that could have caused his symptoms.

But the city’s health department issued a statement on Monday saying that after consulting with Mount Sinai and the Centers for Disease Control and Prevention in Atlanta, “the health department has concluded that the patient is unlikely to have Ebola. Specimens are being tested for common causes of illness and to definitively exclude Ebola. Testing results will be made available by C.D.C. as soon as they are available.”

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