Drug resistant TB: the 'forgotten disease' fights back

March 20, 2007

In the time it takes you to read this sentence out loud, someone somewhere in the world will have died of an illness that has been readily curable for half a century.

That relentless tally will rise to 1.6 million people over the course of a year, making tuberculosis the deadliest infectious disease on the planet after AIDS and ahead of malaria, according to the UN's World Health Organisation (WHO).

On Thursday, the WHO will release a major report on tuberculosis two days ahead of World TB Day, with a special focus on 22 "high burden countries," eight of them in Africa.

There will be some good news.

The worldwide epidemic of TB seems to have peaked; new, more effective drugs are in the pipeline; and many countries have met 10-year targets for detection and treatment.

India and China in particular, experts say, have made measurable strides in curbing infection and reducing mortality.

But progress in checking the disease's spread is severely threatened, the same health officials add, by new strains impervious to some or all of the arsenal of drugs currently available.

Another peril is the HIV/AIDS epidemic, which weakens the human immune system, creating a hospitable environment for what was once aptly called the "wasting disease" or "consumption."

The number of countries in which so-called extensively drug resistant TB -- XDR-TB for short -- has surfaced nearly doubled from 19 to 35 in only a year, including newly reported outbreaks in South Africa and ten nations in Europe.
"The level of resistance in XDR-TB seriously reduces treatment options, resulting in high rates of treatment failure and consequent mortality," Paul Nunn, coordinator of the WHO's TB/HIV and Drug Resistance programme, said recently.

If the problem is not tackled now, he warned, the world will witness "the replacement of the current global epidemic of mostly drug-susceptible TB with multi-drug resistant or XDR disease, and the need to solve a human catastrophe at vastly greater expense."

While the numbers remain paltry compared to the incidence of tuberculosis as a whole, of the 27,000 confirmed cases of XDR-TB reported in 2005, 16,000 -- 60 percent -- proved fatal.

Of the 420,000 cases of the somewhat less virulent multi-drug resistant TB (MDR-TB), almost one in four was mortal.

Overall, there are eight to nine million new cases of tuberculosis, all types combined, every year.

Current treatment for TB, developed more than four decades ago, is difficult to administer and requires six to nine months of therapy.

When patients fail to complete a treatment, the germ Mycobacterium tuberculosis that causes the disease develops a resistance to the drugs to which it has been exposed.

With an estimated two billion people carrying a latent form of the infection -- one out of every three people on the planet -- the risk of exposing vulnerable populations to highly pathogenic forms of a disease that spreads through the air, as with the common cold, has sounded alarms among health professionals.

"The fact that there are essentially untreatable forms of TB in the community is very worrisome," Richard Chaisson, a professor at John Hopkins University in Baltimore and a leading authority on XDR-TB, commented by e-mail.
"Urgent measures are needed."

Posing an additional challenge is the overlay of TB and HIV/AIDS, especially in sub-Saharan Africa.
"Africa has the highest rates in the world of HIV/AIDS infection, and those rates have fuelled the TB resurgence. People who have compromised immune systems are much more vulnerable," said Melvin Spigelman, Head of Research and Development at the New York-based TB Alliance, which leads the world in developing new drugs to fight the disease.

Nearly 200,000 people living with HIV died for TB in 2005 alone, he pointed out. Curing patients who have both diseases is hampered by the incompatibility of drugs considered essential for each illness, giving rise to a highly dangerous condition known as IRIS, for immune-reconstitution inflammatory syndrome.

If tuberculosis seems like a 19th-century illness to many people in the West, it is partly the dated association with artists and writers taking cures in Alpine sanatoria. The main reason, though, is that the disease was largely eradicated in industrialized nations by antibiotics after World War II.

But it has never ceased to plague the developing world. "It is the quintessential disease of the poor," said Spigelman.

"It is the poor nations in general that have the highest incidence of the disease, and even in developed countries -- the US and Britain, for example -- it is the poor who are affected," he said.

And because society's most impoverished members do not have the clout to plead their case, Spigelman added, "it has become a forgotten disease."