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Study chronicles drug-resistant TB

In the U.S., unlike much of the developing world, new cases have declined sharply over the last 15 years.

November 12, 2008|Mary Engel | Engel is a Times staff writer.

At least 83 cases of the most drug-resistant form of tuberculosis were diagnosed in the U.S. in the last 15 years, according to the most thorough accounting to date of the global scourge's national impact.

But unlike what is happening in much of the developing world, new U.S. cases, already low, have declined sharply over that period, from a high of 18 in 1993 to two in 2007.

Tuberculosis experts hailed the trend, reported Tuesday in the Journal of the American Medical Assn.

"Not to diminish the concern, but those numbers are very positive," said Dr. Michael Iseman of the National Jewish Medical and Research Center in Denver, a leading TB treatment center. "They're testament to the quality of TB control in America."

Once a leading cause of death in the U.S., TB cases overall began steadily declining with the development of antibiotics in the 1940s and 1950s.

But from 1985 to 1992, the disease that everyone thought was on the way to extinction staged a comeback.

The resurgence coincided with the beginning of this country's HIV epidemic. By suppressing the immune system, AIDS leaves people susceptible to other infections, including TB.

It also coincided with an increase in immigration from developing countries and with federal cuts in public health funding, according to study author Dr. J. Peter Cegielski of the Centers for Disease Control and Prevention.

It was about this time that drug-resistant TB emerged.

Regular TB, which is diagnosed with a chest X-ray and sputum culture, is curable, but the treatment is not easy. Antibiotics must be taken for six to nine months.

It's standard for patients to be monitored by public health workers to make sure that they take all of their medicine. Failure to complete treatment can give rise to resistance.

Even the resistant strain is treatable with the right antibiotics, but treatment lasts two years or more and costs 100 times as much.

The national study found about 3,000 confirmed cases of multidrug-resistant TB, or MDR-TB, and 83 cases of the most resistant strain.

For the rarer and more dangerous extensively drug-resistant strain, or XDR-TB, half of those treated don't survive -- about the same mortality of regular TB in the pre-antibiotic era.

XDR-TB wasn't given its official name until 2005, although clinicians and laboratories in various parts of the world had identified it in their practices well before then.

Before 1998, most of the XDR-TB cases in the U.S. were people with HIV.

California and New York have the highest levels of drug-resistant tuberculosis in the country, according to the CDC.

A separate study published in August in the journal Clinical Infectious Diseases reported that 18 of the country's 83 cases of XDR-TB were in California. Of the California patients, 83% were foreign-born. Nearly half of those were from Mexico, 20% from South Korea and 13% from the Philippines.

"We're a nation with relatively low TB incidence," said Dr. Ritu Banerjee, an infectious disease fellow at UC San Francisco and an author of the California study.

"But extensively drug-resistant TB is a wake-up call. If we don't strengthen TB diagnosis and care, we're going to see escalation."

--

mary.engel@latimes.com

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