One in five homeless people with tuberculosis¹（肺结核） die within a year of their diagnosis², according to a study led by St. Michael's Hospital's Dr. Kamran Khan. And that number remains³ unchanged over the last decade despite recommendations calling for greater improvements in prevention and control of tuberculosis in homeless shelters. A provincial⁴ coroner's inquest into the death of Joseph Teigesser, a homeless man who died of tuberculosis in Toronto in 2001, made 13 formal recommendations. These included provincial funding for a centralized clinic system to provide specialized⁵ care for those with tuberculosis in Ontario and a review and improvement of shelter ventilation（通风设备） systems. However, the work surrounding these two key recommendations has fallen short, the researchers say in the study.

"The treatment of tuberculosis is often complicated by inadequate⁶ housing, substance dependence⁷, language barriers, mental health problems, not to mention the enormous stigma⁸（柱头，耻辱） that comes with this disease," Khan says. "To effectively control tuberculosis, centres with specialized expertise⁹ and resources are needed to address these complex issues."

The 10-year study, published in the March issue of the journal Emerging Infectious Diseases, also found a growing proportion of tuberculosis cases in Toronto's homeless shelters are in immigrants, raising the risk that dangerous drug resistant¹⁰ strains of tuberculosis could enter the shelter system.

The study found nearly 40 per cent of all tuberculosis cases in the homeless were in immigrants. About 56 per cent of all infections in immigrants involved strains that were not known to be circulating in the city, and were likely acquired in other parts of the world where drug resistance is common.

Historically, tuberculosis in Toronto's homeless population was mostly a disease of Canadian-born men. While highly drug resistant tuberculosis is unusual among people born in Canada, it is an emerging threat in many developing areas of the world. If a drug resistant strain of tuberculosis were introduced into the shelter system, it could set off an outbreak that would have serious public health implications and be very difficult to control. Financial resources to manage such an outbreak would dwarf¹¹ the costs of strengthening preventive measures today, the researchers warn.

"There's been a lot of good work on tuberculosis prevention and treatment in the homeless sector¹² in Toronto over the last several years, and ventilation systems in shelters have improved, although dedicated¹³ funds are needed to make further improvements," said Dr. Elizabeth Rea, a study co-author and associate medical officer of health with Toronto Public Health. "But we also need more affordable¹⁴ housing and we need better access to primary and specialized care for vulnerable homeless individuals."

Tuberculosis is a serious, contagious¹⁵ disease caused by a bacterial¹⁶ infection. Once a person is exposed to tuberculosis, the infection can remain dormant¹⁷ for years to decades before becoming active. However, persons with weakened immune systems, including many homeless persons, are at much greater risk of developing the active form of tuberculosis. While most tuberculosis cases are treatable, highly drug resistant strains of tuberculosis can be life threatening and require years of treatment to cure.

"We need to do a much better job in preventing tuberculosis from spreading in this vulnerable population, and in providing timely, effective clinical care for those who are affected¹⁸ by this disease," says Dr. Michael Gardam, co-author and director of the tuberculosis clinic at the Toronto Western Hospital. "We have shown in previous research that treatment in dedicated tuberculosis clinics by experienced staff plays a major role in improving the likelihood of survival from tuberculosis."