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, whose name is being withheld, is under the first U.S. government-ordered quarantine since 1963. He 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.

CDC officials said they are working closely with airlines. Health officials in France said they have asked Air France-KLM for passenger lists, and the Italian Health Ministry said it is tracing the man’s movements.

A spokeswoman for Czech airline CSA said medical checks showed no infections among its crew members who flew with the man. The airline was also contacting passengers.

Health officials said the man had been advised not to fly and knew he could expose others when he boarded the jets. He had a supply of masks to wear for the protection of other passengers, but it is not clear whether he donned them, Cetron said.

The man told The Atlanta Journal-Constitution that doctors did not order him not to fly and only suggested he put off his long-planned wedding. He knew he had a form of tuberculosis and that it was resistant to commonly used drugs, but he did not realize until he was already in Europe that it could be so dangerous, he said.

After he arrived in Rome, health authorities reached him with the news that further tests had revealed his TB was a rare, “extensively drug-resistant” form, far more dangerous than he knew. They told him to turn himself over to Italian health officials and not to fly on any commercial airlines.

Instead, on May 24, the man flew from Rome to Prague on Czech Air Flight 0727. From Prague, the couple left for Montreal the same day, aboard Czech Air Flight 0104, according to CDC officials.

The man then drove into the United States at Champlain, N.Y. He told the newspaper he was afraid that if he did not get back to the U.S., he wouldn’t get the treatment he needed to survive.

The man is now at Atlanta’s Grady Memorial Hospital under the first federal quarantine order since the government quarantined a patient with smallpox in 1963.

A spokesman for Denver’s National Jewish Hospital, which specializes in respiratory disorders, said Wednesday that the man would be treated there. It was not clear when he would arrive.

The man’s wife tested negative for TB before the couple’s trip and is not considered a public health risk, health officials said.