It is an epidemic of unprecedented proportions—the single most deadly infectious disease in the world. It is the principal killer of people with human immunodeficiency virus (HIV), and claims the lives of more women than all the causes of maternal mortality combined. It is not AIDS, nor hepatitis, nor malaria, but an ancient disease thought 15 or 20 years ago to be on the verge of eradication: tuberculosis. And by all accounts, it is getting worse. Last year, TB killed almost three million peopleemdash; more than in any year during a global epidemic at the turn of the century. According to the World Health Organization (WHO), one-third of the world’s population now carries tuberculosis bacteria, and at current rates as many as 500
million people will become sick from it in the next 50 years. Worse, new strains of the bacillus that are resistant to drug therapy are raising the possibility that, in the not-so-distant future, TB may again become incurable.
On the surface, it seems a relatively benign disease. Tuberculosis is transmitted through the air, in the sputum of a full-blown TB sufferer. But only about 10 per cent of people infected ever develop active, infectious tuberculosis. The highest-risk groups are the world’s poor and homeless, as well as those with undeveloped or suppressed immune systemsemdash; children, the elderly and HIV-positive people. The irony is that, although active tuberculosis is lethal in half of untreated cases, a cureemdash;typically a minimum six-month program of the antibiotics isoniazid, rifampicin, pyrazinamide and streptomycin, costing as little as $11 per patientemdash;has been available for more than 40 years. “It is a totally curable disease if it is treated promptly and with careful supervision,” says Dr. E. Anne Fanning, director of TB services for the Alberta ministry of health. “And it’s cheap to treat.”
But that may be one of the problems. Especially in developing countries, the treatment is
often haphazardly prescribed, and patients, beginning to feel better, stop taking the drugs before they should. The result: the TB bacilli survive and mutate, becoming a tenacious, more deadly form of the disease. WHO estimates that 50 million people are already infected with drug-resistant TB. And many of those carry multi-drug-resistant (MDR) tuberculosisemdash;untouchable by two or more of the standard drugs. In developing countries, where the vast majority of MDR TB cases have occurred, it is usually fatal.
Canada has a relatively good record in TB control. Since 1989, the rate of active cases has remained steady at about 7.2 per 100,000 populationemdash;compared with 9.8 in the United States and 300 in India. However, TB is ravaging Canada’s aboriginal community, with the incidence among status Indians at 47 per 100,000 in 1993. Dr. Howard Njoo, director of TB control at Health Canada’s Laboratory Centre for Disease Control, says that drug-resistant tuberculosis occurs in less than 10 per cent of Canadian cases, and MDR strains even less frequently. But the threat of an outbreak of MDR tuberculosis persists. “I don’t want to sound alarmist,” says Njoo, “but we recognize that this is a global problem.” Foreign-borne cases continue to slip through the cracks. Toronto respirologist Monica Avendaño says the bulk of her TB patients come from Vietnam and Somalia, many of them refugees who were never screened before entering the country. “Canada attracts people from all over the world, especially from developing countries ravaged by war,” says Avendaño. “The screening of those people should be better and more timely.”
In the face of the global epidemic and the rise of resistant strains, research companies are exploring a potential solution: a TB vaccine. But Frank Holler, president and CEO of ID Biomedical Corp. of Burnaby, B.C., which for the past four years has been developing such a drug, estimates that it will be at least six or seven years before a vaccine is available. Meanwhile, the days of government officials in the West confidently predicting the eradication of tuberculosis are long gone. "It was going to be erased by the year 2000," scoffs Avendaño. “But I guess the big shots forgot the way that TB hangs on, and they forgot that the world is not limited to North America, thank you very much.”
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