ATLANTA - Health officials in North America and Europe sought passenger lists Wednesday for two trans-Atlantic airline flights in their effort to find about 80 people who sat near a man infected with a dangerous drug-resistant form of tuberculosis.

Authorities also disclosed that the man was on several flights between various European locales over the course of two weeks earlier this month. Passenger lists for those flights were also being tracked down, they said.

"The investigation is just beginning. It's very challenging," said Dr. Martin Cetron, director of the Centers for Disease Control and Prevention's division of global migration and quarantine.

The man, who is under the first U.S. government-ordered quarantine since 1963, told a newspaper he flew from Atlanta to Greece for a wedding and then traveled to Italy for a honeymoon. Later he flew back to North America because he feared he might die without treatment in the United States.

"Is the patient himself highly infectious? Fortunately, in this case, he's probably not," CDC Director Dr. Julie Gerberding said. "But the other piece is this bacteria is a very deadly bacteria. We just have to err on the side of caution."

The man continues to feel well and shows no symptoms, Cetron said.

CDC officials are concentrating on the trans-Atlantic flights, when the likelihood of spreading the disease was greatest because he was in a confined space with other people for hours.

The CDC was trying to contact 27 crew members from the two trans-Atlantic flights for testing and about 80 passengers who sat in the five rows surrounding the man.

Other passengers on the flights are not considered at high risk of infection because tests indicated the amount of TB bacteria in the man was low, Cetron said.