Deadly New TB Strains Expose the Need for New Drugs, Diagnostics

This week, global TB experts are meeting to discuss how to combat a deadly new strain of tuberculosis, extremely drug-resistant TB (XDR-TB). On Monday, doctors, scientists, and public health specialists met in Paris to address the urgent need for better diagnostics, new medicines, and an effective vaccine. These issues will come up again later this week at the annual Union World Conference on Lung Health, also in Paris.

A CDC and World Health Organization survey of laboratories on six continents from 2000 to 2004 found that one in 50 TB cases was XDR-TB, meaning it is resistant not only to first-line TB drugs, but also to many medicines that represent the last line of defense. XDR-TB is essentially incurable with existing antibiotics.

For XDR-TB patients co-infected with HIV/AIDS, the disease has progressed at an alarming pace with a mortality rate approaching 100 percent. With high HIV/AIDS prevalence rates across Africa, treating XDR-TB will prove vexing.

"The problem of [XDR-TB] is a very rude wake-up call. We don't know how frequently this occurs in different parts of the world," said Kenneth G. Castro, director of CDC's TB elimination program. Speaking at Monday's conference, which was hosted by the Global Alliance for TB Drug Development, Castro called for rapid surveys to determine the prevalence of XDR-TB.

An analysis released by Doctors Without Borders on Monday suggested that most of the TB drugs currently in development are too similar to existing compounds and will likely be less effective in fighting resistant strains. The volume of TB drugs being developed is still "small compared to the drug pipelines for diseases of major concern to wealthy countries, such as cancer or cardiovascular disease," the analysis noted. DWB urged more financial support for the TB alliance and similar efforts.

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