YELLOWKNIFE - Health officials are testing hundreds of Yellowknifers who may have been exposed to tuberculosis.

RCMP Cpl. David Hamilton was tested for tuberculosis a couple of months ago. Hundreds of people in Yellowknife have been tested for the disease after a Yellowknife man was found to have an infectious case of TB. - Jessica Klinkenberg/NNSL photo NWT tuberculosis cases 2001-2006: 2001 - 8 2002 - 4 2003 - 12 2004 - 10 2005 - 8 What is tuberculosis? Tuberculosis (TB) is a respiratory disease caused by a bacterium. Someone with an active, untreated case of TB can infect others through sneezing, coughing, speaking, kissing, or spitting. People infected with TB whose immune systems are strong enough to keep the bacteria at bay are said to have latent (or inactive) TB, and are not infectious. Ninety per cent of people infected with TB are latent, non-infectious cases. Most will never develop active TB. How is it tested for? In a tuberculin skin test, a small sample of TB antigens is injected under the skin on a patient's arm. If the skin reacts within two days, that means the patient has antibodies for TB, indicating exposure to the disease. It does not indicate whether the infection is active or latent. Chest X-rays help with further diagnosis. What are the symptoms? Active tuberculosis can feel like a regular cold, but with a persistent cough that lasts longer than three weeks, chest pain and sometimes coughing up blood. Tuberculosis can be mistaken for pneumonia. A Fort McPherson woman died from misdiagnosed TB in July 2000. How is it treated? Left untreated, active tuberculosis (also known as consumption) is fatal in about 50 per cent of cases. Today patients with active TB follow a nine-month regimen of antibiotics to eradicate the bacteria.

Chief Medical Officer Dr. Andre Corriveau said a man in the city was diagnosed with an infectious case of TB in March.

The number of people who have had to be tested is uncertain, but it's believed the man stayed for a while at the Salvation Army homeless shelter.

"I haven't seen the final tally; it was a few hundred people that had to be followed," said Corriveau. "It's not just homeless people, they were part of the crowd that had to be followed."

He said his department made a "judgment call" in not alerting the public, but said he feels it was the right decision.

"There's always a balance between alarming people when there is no reason to do so and not putting a stigma on a population that's already kind of marginalized," said Corriveau.

"At this point, I don't have any concern that people might've have been unduly exposed to something and weren't contacted."

Corriveau revealed that residents in 23 NWT communities may have been in contact with the individual tested as well.

"We define close contact (as being) people that live in the same house, or they share the same breathing air for more than four hours. There's people in the shelters that had to be followed up."

A TB infection can take up to six months to develop and requires nine months of antibiotic treatment to cure.

"If you end up treating 15 or 20 people, that's a lot of work," said Corriveau.

The man with TB is being treated in a hospital in Edmonton.

"They have to be kept in the hospital until they're not infectious anymore," said Corriveau.

Corriveau said the Yellowknife man is not infected with a drug-resistant strain of TB.

Const. Roxanne Dreilich, with the RCMP's community policing unit, said about 50 officers were tested.

"We all had to go for testing within the last six or eight weeks regarding a person who has been in custody a number of times who has been identified as having TB," she said.

Dreilich said a second round of tests is coming up.

"(Possibility of coming into contact with infectious diseases is) certainly something we're told about when we go through our training," she said. "It's sort of understood that that's part of the job."

Dreilich said that so far no one has reported being infected with TB yet.

Deputy fire Chief Chucker Dewar said fire department personnel were also tested six to eight weeks ago for TB.

"We met with Stanton infection risk people to see what our risk level was," he said.

Corriveau said the most of the people health officials need to follow up with are homeless.

"We're confident no one is going to be missed," he said. "Sometimes it may be more difficult to offer treatment to people with no fixed address."

Corriveau said that the man with TB had not travelled outside of Yellowknife, but that he had come into contact with people from out of town who have since returned to their communities. For confidentiality reasons, Corriveau would not say which communities.