Fear factor. (John Spink/AP Photo)

The most recent healthcare worker to contract Ebola flew on a commercial airplane shortly before being diagnosed. Even though authorities say it's unlikely she infected any of the 132 other passengers on the flight, the specter of Ebola being spread in the skies has already helped send down the stocks of the country's major airlines.

As of 2:50 pm on Wednesday, no doubt in response to the news, virtually every major air carrier had seen its stock drop. Shares of American Airlines had fallen nearly 1.5 percent (though they have since recovered, and closed half a percentage point up on the day), Delta had dropped by almost 2 percent, United Continental had dipped by more than 3.6 percent on the day, and Spirit Airlines had tumbled by roughly 3 percent.

The dip, though particularly pronounced today, actually spans back to the beginning of the month--tracking pretty closely with rising concerns about Ebola continuing to spread. 

American Airlines' stock has fallen by 15 percent since the beginning of October.

Delta's has tumbled by 13 percent over that same period.

United Continental's has fallen by 14 percent.


Spirit Airlines' by 21 percent.


And Southwest Airlines' by 13 percent.

Why the healthcare worker was allowed to fly is still unclear—she had been in recent contact with an Ebola patient, which should have prevented her from boarding a plane, according to the Centers for Disease Control and Prevention. Thomas Frieden, the director of the CDC, expressed his surprise in a statement this afternoon. "She should not have flown on a commercial airplane," he said.

But that merely underscores the reason people might think twice about flying now. As my colleague Mark Berman points out, there were 50 other health-care workers who entered the infected patient's room, some of whom might have traveled or moved around in recent days. Extrapolate that uncertainty to include the scores of other medical workers who have attended to patients in Spain and Africa—and it's enough to make people feel nervous about flying.

In 2003, when severe acute respiratory syndrome (SARS) began spreading in Asia, the news devastated the Asian airline industry. But there's one big difference that flyers should keep in mind. It's possible that SARS can be spread through airborne routes. That is not the case with Ebola.

U.S. airline stocks fell on Wednesday after a second Texas health-care worker with Ebola had reportedly traveled on a commercial flight the day before being diagnosed. (Reuters)