As health officials contact passengers who travelled with a man with a dangerous form of tuberculosis, questions are being raised about how he was able get into Canada andthentheUnited States.

The infected man, from Atlanta, told a newspaper reporter that he knew when he left Europe that he had extensively drug-resistant tuberculosis, or XDR-TB, but that heand his wife decided to sneak back into the U.S. via Montreal.

Of the 28 passengers who werenear the man on seat 12 C of Czech Airlines Flight 0104 from Prague to Montreal on May 24, health officials have tracked down 16.

Health authorities want to speakto about 27 crew members and 80 passengers who are considered most at risk because they sat within two rows of the man, but stress the risk of infection is low.

The man is now under a federal isolation order in the U.S.

"He is still well and continues to be asymptomatic," Dr. Martin Cetron, director of the U.S. Centers for Disease Control's division of global migration and quarantine, told a news conference Wednesday. "He is currently still in isolation, and in an Atlanta hospital and under the care of infectious disease specialists."

It appears the man never felt ill with the virtually untreatable disease, according to Alison Young, a reporter with the Atlanta Journal-Constitution who contacted the man at his hospital room.

"He says he does not have any symptoms," Young told CBC Radio. "He has no coughing. In fact, he says he is perfectly healthy and the disease was only discovered when he was tested for something else. They noticed a spot on one of his lungs."

He didn't initially realize that his tuberculosis was resistant to drugs until he was called by the CDC during his honeymoon in Rome. The CDC told him to turn himself in to Italian authorities, isolate himself and get treated. CDC also told him he couldn't fly aboard commercial airlines.

"I thought to myself, 'You're nuts.' I wasn't going to do that. They told me I had been put on the no-fly list and my passport was flagged," the man told the newspaper, declining to be identified because of the stigma of the diagnosis.

By the time U.S. health officials tracked him down at a hotel in Rome, he had already left for Montreal, saying he did not believe the Italian medical system could treat his infection.

"It's regretful that we weren't able to stop that," Cetron said of how the man fled Rome. "There will be many lessons learned from this."

The man told the paper he and his wife decided to sneak back into the U.S. via Canada.

While the CDC was working to inform international counterparts, the man phoned them from New York, where U.S. authorities placed him in isolation. The CDC said it relies on a "covenant of trust," and there is not much it can do when someone breaks the trustwhile overseas.

Canadian border authorities said if they had been warned, the man would have been detained in Montreal.

In a statement Wednesday, Czech Airlines said itnotified Canadian and U.S. health authorities when it learned it had a passenger on board thought to be infected with XDR-TB, and handed him over to local health officials when the plane arrived in Montreal.

An official withthe Public Health Agency of Canada disputed that, sayingthere is no record of the pilot notifying quarantine services at Montreal's Pierre Elliott Trudeau International Airport that they should meet the plane.

"Under the Quarantine Act, there is a requirement for advance notification, so the pilot, if he or she becomes aware of an ill passenger on board, is required to report ahead and cause one of our quarantine officers in our quarantine program to be aware of the situation," said Dr. Howard Njoo, director-general of the Public Health Agency of Canada's centre of emergency preparedness and response.

"That did not happen in this case, because we checked with our quarantine station in Montreal. There was no advance notification by the pilot of a situation of an ill passenger on board."

U.S. customs officials said they are reviewing the decision to allow the man to re-enter the U.S. without immediately being in isolation.

Tuberculosis is caused by Mycobacterium tuberculosis. It poses a public health threat because it is contagious and spreads through the air. It affects thelungs and may leadto symptoms such as chest pain and coughing up blood.

Health officials estimate about half of cases of XDR-TB are fatal. They say XDR-TB resists more than the first- and second-line drugs normally used to treat infection.