The $2 trillion U.S. travel industry is nervously keeping an eye on the worst Ebola outbreak in history, hoping travelers don’t rein in their spending ahead of Thanksgiving.

Already, the deadly disease is having an effect:

On Wednesday, the day a Liberian man died of Ebola in the U.S. and tighter airport screening was announced, airline stocks dropped as much as 3.6 percent while U.S. stock markets overall finished strong. That comes on top of a 4 percent drop for an index of global airline stocks in September. An international airline trade group cited Ebola as a key reason for the decline.

The world’s largest cruise line, Carnival Corp., has changed the itineraries of two ships that were scheduled to land in ports near disease-ravaged West African countries. Another cruise line is considering doing the same.

More than 7 million Americans are expected to travel by air during the busiest travel days of the year — the Wednesday before Thanksgiving and the Sunday and Monday afterward.

For now, at least, travel agents and other industry experts say they have heard of no widespread travel cancellations out of fear of catching the disease on planes or cruise ships or in hotel rooms.

So far the disease has been limited in the U.S. to Thomas Duncan, a Liberian man who died Wednesday of Ebola after traveling to Texas.

Travel industry officials say additional infections in the U.S. could upset vacation plans.

“I have no doubt there will be some people that won’t travel, but it won’t be big numbers unless something happens between now and December,” said Diane Embree, a Los Angeles travel consultant.

To keep the disease from spreading, federal officials Wednesday announced new screening procedures for international travelers arriving at these airports: John F. Kennedy International in New York, Newark Liberty International in New Jersey, Washington Dulles International, Chicago’s O’Hare International and Hartsfield International in Atlanta.

“We have not yet heard any concerns that travel demand will be hurt by this situation, and are hopeful that will remain the case so long as reactive steps remain careful and balanced,” said Jonathan Grella, a spokesman for the U.S. Travel Association, the trade group for the travel industry.

Representatives from Orbitz and Travelocity, two of the largest travel booking sites, say they have seen no drop in bookings to suggest travelers are fearful of flying this holiday season.

Carnival Corp. said the Ebola outbreak has prompted a change in the ports of call of ships from two subsidiary cruise lines.

Instead of making stops in West Africa, the Seabourn Sojourn’s South Africa Line Voyage, departing from Spain on Nov. 19, will drop anchor in Malaga and Cadiz, Spain. Holland America’s 35-day African Explorer Cruise will cut out West African ports and instead stop at the Isle of Sao Vicente in Cape Verde and Tangier, Morocco.

Princess Cruise Lines is also considering rerouting its 30-day “West Africa Adventure.”

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