DALLAS — The airline passenger who brought Ebola into the U.S. initially went to a Dallas emergency room last week but was sent home, despite telling a nurse that he had been in disease-ravaged West Africa, the hospital said Wednesday in a disclosure that showed how easily an infection could be missed. The decision by Texas Health Presbyterian Hospital to release the patient could have put others at risk of exposure to the disease before he went back a couple of days later, when his condition worsened. A day after the man’s diagnosis was confirmed, a nine-member team of federal health officials was tracking anyone who had close contact with him after he fell ill on Sept.