The Centers for Disease Control expanded precautionary efforts Thursday night by reaching out to passengers on an earlier flight that Ebola patient Amber Vinson took before she had reported any symptoms of the virus.

The CDC said anyone on Frontier Airlines flight 1142, which flew from Dallas to Cleveland on Oct. 10, should call the agency at 800-CDC-INFO (800-232-4636). Amber Vinson, the second nurse to test positive with Ebola in the U.S., took that flight after taking care of the U.S.’s first diagnosed Ebola patient, Thomas Eric Duncan, who died on Oct. 8.

The passengers will be interviewed by CDC officials about the flight and about any potential symptoms they may have developed since flying. “Individuals who are determined to be at any potential risk will be actively monitored,” the CDC said in a statement about the notification.

Ebola is transmitted by an infected person when that person is symptomatic, and only through direct contact with that individual’s body fluids, which include blood, saliva, vomit or diarrhea. Vinson had a slight fever of 99.5 degrees before flying Oct 13 from Cleveland to Dallas. CDC director Dr. Tom Frieden said that passengers on the flight from Cleveland back to Dallas were being notified out of an abundance of caution. He said that they were at very low risk of exposure since Vinson presumably did not vomit or spread body fluids during the flight.

Now the agency says, “Based on additional information obtained during interviews of close contacts to the second healthcare worker from Texas Presbyterian Hospital who tested positive for Ebola, the … CDC is expanding its outreach to airline passengers now to include those who flew from Dallas/Fort Worth to Cleveland on Frontier flight 1142 on Oct. 10.”

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