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Passengers who may have been exposed to infectious TB on at least 15 long-haul flights into and out of Canada were never notified because airlines failed to share information with federal health officials, The Globe and Mail has learned.

A Public Health Agency of Canada report obtained under Access to Information legislation says the unnamed airlines either refused or failed to provide manifests and other passenger details on more than a quarter of the flights it investigated for possible tuberculosis exposure between 2006 and 2007.

Following international guidelines, PHAC normally identifies passengers who sat in the five rows around an infectious patient. Letters are sent via local public health authorities to these "contacts" to recommend a follow-up skin test.

Without passenger information, contacts weren't identified and no letters sent. The agency opted against other measures, such as going public with flight details.

The report, which notes a dramatic increase in the number of such cases in Canada, raises questions about Ottawa's ability to manage, track and control the spread of TB and other types of contagion on airplanes. The agency insists there was little risk to passengers, that problems with information-sharing no longer exist, and that airlines have fully co-operated this year on 40 new aircraft-related TB cases - though there is no legal requirement for them to do so.

The chance of contracting TB on an aircraft is very low. Only passengers within the immediate vicinity of an infected patient are at risk, and only after prolonged exposure. But the World Health Organization has urged increased vigilance due to the explosion of international air travel, the prevalence of the disease in the developing world and the emergence of drug-resistant strains.

That risk was drawn in sharp relief in May, 2007, when an Atlanta man flew to Europe to get married despite being told he had multidrug-resistant TB, an especially dangerous strain defined by its resistance to at least two powerful antibiotic drugs used in treatment.

Andrew Speaker's case made international headlines as health officials in several countries issued public appeals for passengers to get tested if they had sat near him on one of several flights.

"I was shocked and scared," said Nassim Tabri, 28, a graduate student who sat one row in front of Mr. Speaker on a flight to Montreal from the Czech Republic. He is one of nine plaintiffs in a $700,000 lawsuit filed against the man for pain and suffering.

Mr. Tabri said he endured sleepless nights, self-imposed isolation, frightening Internet searches and a delay in his studies as he waited more than two months to learn if he had been infected. His final skin test was negative.

"I had to wait for nine weeks for testing and I was held hostage to that," he said, referring to the time it takes for TB to take hold in the body. "I felt really bloody violated. At the same time, I felt helpless. Why is this happening? There's nothing I could do about it."

Most of the plaintiffs in the continuing Speaker lawsuit tested negative for TB. A few were positive, but it's uncertain if it's the same strain. None of their allegations has been tested in court and Mr. Speaker has yet to file a statement of defence.

It turns out these passengers were not alone; Canada was quietly investigating dozens of similar cases at the same time.

From Jan. 1, 2006, to Dec. 31, 2007, the PHAC was notified by provincial health authorities of 53 cases of TB with a history of air travel in Canada - a significant increase from the 19 total cases it received over the previous four years.

The majority of the cases, 58 per cent, were moderately to highly infectious; three cases were drug-resistant, including two cases of multidrug-resistant TB. Nearly all infected patients, 94 per cent, were foreign-born.

The agency whittled down a list of 105 affected flights to 59 that required passenger-contact tracing based on WHO guidelines. Those protocols rule out all but the most serious cases: It must be likely the patient was infectious at the time of travel, the flight must have occurred within the past three months and it must have lasted longer than eight hours. (Canada goes a step further by tracking all cases of laryngeal and multidrug-resistant TB regardless of flight duration.)

The airlines, which the agency won't name, failed to make available information on 15 of the 59 identified flights.

"For five of these flights, no response was ever received from the airline despite repeated attempts by TBPC [Tuberculosis Prevention and Control] staff," the report notes.

"In one case, a subpoena was requested by the airline before they would release any passenger information. This request was addressed by TBPC but to date no further response has been received from the airline."

For another three flights, the responsible airlines preferred to contact passengers themselves and refused to hand over manifests, the report states. On other flights, passenger names couldn't be found or manifests were missing, including two that had been purged from the airline's computer system.

Even when there was co-operation, there were problems. "For three flights, the details provided on the manifest were not sufficient for contact tracing and further information has been requested and remains pending," the report notes. No seating information was provided for one flight, which meant all passengers had to be contacted.

The agency was still waiting for passenger manifests from two more flights at the time the report was written on Jan. 16, 2008.

Dr. Howard Njoo, director-general of the agency's Centre for Communicable Diseases and Infection Control, stressed there was little risk of disease transmission on the flights in question. Although the cases involved active TB, the agency determined they weren't contagious enough to warrant a public alert, he said.

Dr. Njoo said there are other means to track down passengers without manifests, including customs declaration cards. He said he didn't know how many people on the 15 flights were traced this way. But when pressed, the agency later confirmed none was.

"If they don't know where the passenger was seated, then they have to contact the whole airplane," said Dr. Claude Thibeault, a former medical director for Air Canada and now medical advisor to the International Air Transport Association (IATA). He serves on the WHO panel that wrote the guidelines for handling TB cases on aircraft.

Dr. Thibeault said some airlines have been reluctant to share information because of privacy concerns and conflicting domestic and international regulations. "This issue is being discussed everywhere. It's not malicious and there's nothing to hide from the airlines' standpoint, it's purely a legal issue," he said.

Another problem is that carriers aren't typically notified of TB cases until several weeks or months after the flight, by which time their computer systems have been purged of much passenger information, he said.

The jury's still out on the value of contact tracing, he added, noting some countries — especially those with limited resources and where TB is endemic — prefer to focus on actual cases rather than potential transmission.

Dr. Njoo concurs that Canada runs one of the most proactive TB surveillance programs in the world. "Our criteria for even identifying a particular flight and trying to get information to contact fellow passengers at risk within the five rows would be considered cutting-edge compared to many other countries," he said. He attributes the year-over-year increase in cases to better co-operation with the provinces.

An-Lac Nguyen, the lawyer representing passengers in the Speaker lawsuit, said he agrees with PHAC's decision not to go public with the flights for which it had no passenger information. "The fact is, TB is not that easily contracted and there's an alarming effect of making a public announcement," he said.

But Mr. Nguyen said he would like to see health authorities make the public better aware of the risks and to "be more forceful in forbidding people from flying when there's real danger."

Unlike Canada, the U.S. has maintained a national "Do Not Board" list since June 2007 that prevents passengers with serious infectious diseases from boarding commercial aircraft departing from or arriving within its borders. Names are added by the Centers for Disease Control and Prevention upon review of requests made by public health officials in any jurisdiction.

In its first year, the CDC received 42 requests, including three from Canadian officials. Thirty-three names were added — all because of infectious pulmonary tuberculosis.

Canada handles flight bans on a local, case-by-case basis and only when it's knows a patient intends to fly on a particular airline.

According to the WHO, air quality on board commercial aircraft is high and generally cleaner than the air in most buildings. The risk of TB transmission increases on long-haul flights, but it's similar to that of any other instance when people share an enclosed space for a long period of time, the organization states.

There has yet to be a clinically confirmed case in which a person developed active TB disease after being infected by a fellow airplane passenger. However, there are documented cases from the early 1990s of airline passengers and crews acquiring the infection while on long flights, including multidrug-resistant TB.

Tuberculosis screening is mandatory for immigrants and refugees to most countries, including Canada, but it is not required for the vast majority of airline passengers.