TORONTO - There's no cause for concern because only eight of 27 passengers on a bus that carried a rider infected with tuberculosis have come forward, Ontario health officials said Thursday.

An appeal was issued last week for 27 passengers of Greyhound bus trip 0367 from Toronto to Detroit on Aug. 31 who disembarked in Windsor, Ont., to get tested for the disease.

Health Ministry spokesman Mark Nesbitt said Thursday the eight people are being assessed to determine whether they need a skin test for tuberculosis.

"If they do need a skin test, they'll get one of those, and those take two or three days to come back because it's a reaction issue," Nesbitt said.

"It's like an allergy test, it's an antibody test, basically a very tiny little injection, and then they check two or three days later for a reaction."

Nesbitt said he isn't worried by the low number of passengers that have come forward to be tested.

"Generally it's going to take three to eight weeks for a skin test to be worthwhile doing," he said. "It takes that long for any sort of antibodies to build up to be able to detect this."

Nesbitt said he had no information as to where the eight passengers are from.

The ministry continues to appeal to the other 19 passengers to contact their local health unit or call their hotline number at 1-866-532-3161, Nesbitt added.

The Greyhound bus left Toronto at 12:30 p.m. on Sunday, Aug. 31, with 33 passengers aboard. The bus stopped in London, Ont., at 2:35 p.m. and nine more passengers got on. The bus arrived in Windsor at 5:05 p.m.

The infected person -- who was only identified as a woman carrying a Canadian passport and ranging in age from 20 to 45 -- had previously tested positive for tuberculosis in the United States and was refused entry back into U.S. at the Detroit border.

It's unknown whether doctors warned her against travelling.

The woman doesn't have the more serious forms of multi-drug resistant or extensively drug-resistant tuberculosis. She was put into quarantine.

The remaining passengers who were still on the bus are being looked after by public health officials in the U.S. and Ontario, but it's still too early too know if they were infected.