May 30 (HealthDay News) -- U.S. health officials are looking for airline passengers who may have been exposed by a fellow passenger to a highly drug-resistant and dangerous strain of tuberculosis.

The passenger had been diagnosed with tuberculosis and advised not to travel. But on May 13, he flew from Atlanta to Paris, continued on to Prague, then took a return flight to Montreal on May 24, before driving back into the United States.

"On May 13th, the patient departed on Air France fight 385 from Atlanta and arrived in Paris," Dr. Julie Gerberding, director of the U.S. Centers for Disease Control and Prevention, said during an afternoon teleconference. "The patient returned in Czech Air flight 0104 to Canada, then entered the United States by car."

After returning to the United States, the man was contacted by the CDC and asked to check himself into the isolation ward of a New York City hospital, which he did. On Monday, he was flown home in a CDC plane to Atlanta, where he remains hospitalized.

The man was infected with "extensively drug-resistant" TB, also called XDR-TB, which resists many drugs used to treat the infection.

"This patient may have been a source to the passengers," Gerberding said. "The passengers most likely to be at risk would be the passengers who were seated immediately close to the patient," she added.

Passengers on both flights came from many countries and states, Gerberding said.

Gerberding said the CDC is working with local health officials to identify passengers on the two jetliners. She advised that these passengers be tested for tuberculosis.

The CDC is also asking the local health officials to notify the passengers of their potential risk. "While we don't think that their risk is high, we want to offer them the opportunity to be evaluated and tested," Gerberding said.

Extensively drug-resistant tuberculosis is a subtype of multi-drug resistant tuberculosis that can cause severe illness and death. Like all forms of tuberculosis, extensively drug-resistant tuberculosis is spread person-to-person through the air, usually through vapor droplets. Last year, there were two cases of extensively drug-resistant tuberculosis in the United States, she said.

Gerberding noted that patients with highly communicable diseases such as tuberculosis usually agree to voluntarily limit their travel.

"In this case, the person had compelling personal reasons for traveling and made the decision to go ahead and meet those personal responsibilities," she added.

This is the first time since 1963 that a federal isolation order has been issued, Gerberding said. Back then, the order was issued to quarantine a patient who had smallpox, she said.