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Doctors are finding more cases of multi-drug-resistant tuberculosis (MDR-TB) than ever, according to a new World Health Organization (WHO) report.

The report, , is based on information collected between 2002 and 2006 on 90,000 TB patients in 81 countries. It is said to be the largest survey to date on the scale of drug resistance in tuberculosis.

WHO estimates there are nearly half a million new cases of MDR-TB diagnosed worldwide each year. That represents about five per cent of all the global new TB cases that emerge annually.

The study also found that extensively drug-resistant tuberculosis (XDR-TB) -- a virtually untreatable form of the disease -- has been recorded in 45 countries. But because so few countries are equipped to diagnose XDR-TB, the report authors say they had limited data to fully assess the scope of the XDR problem.

Tuberculosis is a respiratory disease that can be fatal if left untreated. While it has existed worldwide for centuries, in recent years, the more worrisome MDR and XDR forms of the illness have emerged.

MDR-TB is resistant to at least two of the best anti-TB drugs, isoniazid and rifampicin, which are considered first-line drugs and are used to treat all persons with TB. XDR-TB is resistant to first-line drugs as well as resistant to any fluoroquinolone and at least one of three injectable second-line drugs.

Tuesday's report from WHO found that the highest rate of multi-drug resistance was recorded in Azerbaijan, where nearly a quarter of all new TB cases (22.3 per cent) were reported as multi-drug-resistant.

Other countries with high proportions of MDR-TB among new TB cases included:

• Moldova;
• Ukraine;
• the Tomsk Oblast region of Russia; and
• Uzbekistan

True scale unknown

But the true scale of the problem of drug-resistant tuberculosis remains unknown in some pockets of the world, the WHO authors report. That's because only six countries in Africa - which is thought to be the region with the highest incidence of TB in the world -- were able to provide drug resistance data for the report.

The other countries in the region could not conduct surveys because they lack the equipment and trained personnel needed to identify drug-resistant TB, explained the WHO's Abigail Wright, the report's principal author.

"Without these data, it is difficult to estimate the true burden and trends of MDR-TB and XDR-TB in the region. It is likely there are outbreaks of drug resistance going unnoticed and undetected," she said in a statement.

The global rates of drug resistance that the WHO discovered are the highest they've ever found. Dr. Mario Raviglione, director of the WHO Stop TB Department, says the TB drug resistance issue is a serious one and needs "a frontal assault."

"If countries and the international community fail to address it aggressively now we will lose this battle," he said in a statement.

Resistance to tuberculosis medications occurs when these drugs are misused or mismanaged. If patients do not finish their full course of drug treatment or if health-care providers prescribe the wrong treatment, then the bugs that cause TB can adapt and develop drug resistance.

Raviglione says the key is better and faster diagnosis.

"Programs worldwide must immediately improve their performance in diagnosing all TB cases rapidly and treating them until cured, which is the best way to prevent the development of drug resistance," he says.

TB in Canada

In Canada, it's estimated that about 1,600 cases of TB are diagnosed every year. Only about 1.2 per cent of those cases are multi-drug resistant.

The highest rate of TB diagnoses in this country are among those between the ages for 35 and 44. TB among foreign-born individuals accounted for 64 per cent of all reported cases in Canada in 2006. Canadian-born Aboriginal cases made up 20 per cent, while Canadian-born non-Aboriginals made up another 12 per cent.

Dr. Vernon Hoeppner, of the Division of Tuberculosis Control at the University of Saskatchewan, says because tuberculosis is not common in Canada, many family doctors fail to recognize it, as its symptoms - a persistent cough, fatigue, weight loss - can mimic other illnesses.

Even when a proper diagnosis is made, there is often the challenge of patients complying with treatment. Treatment typically involves taking three medications together for six months. Because the drugs can cause stomach upset or allergic skin reactions, some patients stop taking them. That can lead to drug resistance in both the patient and in the germs that could then transfer to someone else.

Hoeppner says oftentimes, TB patients need to be actively observed to ensure they take their medication. That can increase costs, since health workers need to visit patients at home.

One TB patient Â鶹´«Ã½ spoke to, a man in his mid-20s from Eastern Europe who didn't want his name used, says he spent three months in hospital being treated for his active TB.

"There is no timeline. That is the most difficult thing of being in the hospital. You are in isolation but you don't know when you are getting out," he said.

He is now at home being treated. But even with a degree in economics, he has found it difficult finding work and is still looking for a position in his chosen field of financial services consulting.

Dr. Kamran Kahn, a tuberculosis expert at St. Michael's Hospital in Toronto, says the cost of treating a single patient with MDR-TB can run around $250,000, while the costs of treating a patient with XDR-TB would be over $1 million and last for two years.

Khan says that many of the cases of drug-resistant TB in Canada are diagnosed in recent immigrants.

"Today, we are seeing cases of multi-drug-resistant TB, most of which were acquired overseas and introduced here. As for XDR-TB, that is something we haven't seen much of yet. But if we don't get a good grasp of this problem now we can anticipate we will see more of it in the future," he told Â鶹´«Ã½.

Dr. Michael Gardam, head of the tuberculosis clinic at Toronto Western Hospital, says he worries about what could happen if drug resistance in TB grows.

"We have relatively few drugs that can treat it, treatment can be prolonged. And when you start losing those drugs, it becomes harder and harder to cure someone," he says.

"It's always hard to convince people in Canada that TB is a big issue because we have one of the lowest rates in the world. The point I always make is that if it's happening out there, it will happen here."