MONTPELIER, Vt. - Passengers travelling by bus between Boston and Montreal may have been exposed to tuberculosis but it's unlikely they were infected, Massachusetts health officials said Tuesday.

The passengers of the May trip were being notified that another passenger on the bus had the disease. Dr. Al DeMaria, director of communicable disease control for the Massachusetts Department of Public Health, said these types of notifications of passengers happen "all the time."

"We almost never find anyone with infection as a result," he said.

"There's nothing about this case that suggests he's highly infectious or has a rare kind of tuberculosis," he said of the passenger, who said he travelled roundtrip May 5-8.

Chris Andreasson, general manager of Vermont Transit Co. Inc., said the company's bus drivers had been tested and cleared of the disease.

The Boston Public Health Commission had a Boston passenger and bus driver tested for the disease, but the results were confidential, said spokeswoman Ann Scales.

This spring Atlanta lawyer Andrew Speaker caused an international health scare after he flew to Europe after he had been told he had a drug-resistant form of tuberculosis.

"I think people because of the Speaker case think this is an unusual circumstance, but in fact what was unusual was all the publicity about that case," said DeMaria. "Even with 16 hour plane rides, it's rare we find anyone who's infected."

The Vermont Department of Health was notified last week and determined that no Vermont passengers were on the bus.

Dr. Cort Lohff, Vermont state epidemiologist, said he could not recall a case in Vermont where passengers were notified after a contagious person boarded a bus or plane in the state.