(Reuters) - United Airlines believes the U.S. Ebola patient flew on its aircraft from Brussels to Dallas-Fort Worth via Washington on Sept. 20, based on information it received from federal officials, according to a company spokeswoman.

The U.S. Centers for Disease Control and Prevention said there was “zero risk of transmission” on these two flights because the patient showed no symptoms at the time and therefore could not have been contagious, the United spokeswoman said.

The CDC has said it is unnecessary to contact others who traveled on the flights, she added.

It is not yet known which carrier the patient took from Ebola-ravaged Liberia to Brussels.

“We are ensuring our employees have this information and suggest that any customers who have concerns contact the experts at the CDC for further information,” the spokeswoman added.

The patient flew on flight UA 951 to Washington Dulles and flight UA 822 to Dallas-Fort Worth.

Earlier on Wednesday, airline stocks fell amid concerns that fewer people would travel because of the disease. United Airlines shares fell about 2.8 percent to close at $45.47 in trading before the disclosure that the first person to be diagnosed with Ebola in the U.S. had taken the airline.