Passengers who sat near a fellow traveler with a particularly virulent strain of tuberculosis on flights six months ago have not developed the disease and should not expect to, authorities said Wednesday.
The Public Health Agency of Canada followed up with 29 passengers who sat near the infected traveler on a flight from Prague to Montreal to see if they developed tuberculosis.
The Centers for Disease Control tested dozens more in the United States.
"Six months later, there's been no proof of transmission," said Alain Desroches, spokesman for Canada's public health agency. "That's a good sign at this point."
Of course, he added, there is still a chance of TB appearing later. "We can't rule it out because people can develop symptoms up to two years after being exposed. But we're optimistic."
The agency's analysis is based on information provided by passengers' individual physicians, he noted.
In May, US and Canadian health authorities urged passengers of two Air France and Czech Air flights to be tested for a particularly virulent strain of tuberculosis that may have been spread by a US citizen.
Andrew Speaker, the US lawyer who sparked the global health scare, had traveled on an Air France from Atlanta to Paris on May 12, and on a Czech Air flight from Prague to Montreal on May 24.
US health authorities seized him when he returned from the epic journey and put him in isolation.
Speaker was discharged from hospital in July after being treated for multi-drug-resistant tuberculosis. Surgery on July 17 removed part of his lung.
Doctors said he had defied their warnings not to travel after being diagnosed with the disease.
But after getting married in Greece and honeymooning in Italy, he took a series of flights to escape being committed to a clinic in Europe, eventually returning home via Canada.
Doctors said he would continue to take antibiotics for about two years, and be closely watched by health workers.