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Genetic Analysis Helps Track TB Infection Chain

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Genetic Analysis Helps Track TB Infection Chain

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Genetic Analysis Helps Track TB Infection Chain

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ROBERT SIEGEL, host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.

MICHELE NORRIS, host:

And I'm Michele Norris.

The case of the lawyer from Atlanta with highly drug-resistant tuberculosis put that disease back in the news. And while cases are still rare, the attention has created a new urgency in the effort to stop TB.

NPR's Richard Knox reports on a new tool that's helping officials track down who has the disease and reveal how they got it.

RICHARD KNOX: Dozens of Colorado health workers are very busy right now trying to track down everybody who came in contact with Kalpana Dangol. Dangol died of TB in a Colorado Springs Hospital last Friday. She was a 19-year-old college student from Nepal where authorities think she got TB. Neither she nor anyone else knew she had it until a few hours before she died.

That's unusual. But Dr. Lisa Miller of the Colorado Department of Public Health says it's not unheard of.

Dr. LISA MILLER (Director, Colorado Department of Public Health): Tuberculosis can be difficult to identify. Oftentimes, people don't present with the classic cough, fever, night sweats, weight loss.

KNOX: Now officials are trying to find out if Dangol infected anyone else. They're using what Public health people call shoe-leather epidemiology.

Dr. MILLER: Identifying these contacts, tracking down their location, making sure we screen them for symptoms and give them a skin test, and if necessary, chest X-ray and educate them.

KNOX: TB is often hard to track. School let out in May so many of Dangol's contacts have probably left town. In other cases, people don't want to give their contacts' names. They may not even know them.

Dr. PHIL LeBEAU(ph) (TB expert, U.S. Centers for Disease Control And Prevention): Sometimes you just don't get everyone.

KNOX: Dr. Phil LeBeau is the TB expert at the U.S. Centers for Disease Control and Prevention. He says officials are using genetic fingerprints to track the transmission of TB from person to person.

Dr. LeBEAU: Genotyping is a new tool, which allows us to identify transmission that we wouldn't have been able to identify using the traditional shoe-leather epidemiology.

KNOX: If two people are infected with matching strains and they were at the same place at one time or another, there were part of the same chain of transmission.

Not long ago, genotyping uncovered an unsuspected interstate epidemic that officials traced to a bar near the state line.

Dr. LeBEAU: States themselves would never have figured out that these are related because the states generally don't look at other states' cases.

Dr. PATRICK MUNIN (TB Expert, Centers for Disease Control And Prevention): This happens on an everyday basis at a local level. Country health departments are using this information to make local links.

KNOX: Patrick Munin, another TB expert at the CDC, says in Forth Worth, Texas, genotyping led to a ten-fold reduction in new infections over a two-year period.

Lately, Munin has asked colleagues around the world to search through computer libraries containing hundreds of thousands of TB genotypes. They're looking for one that matches the strain Atlanta lawyer Andrew Speaker apparently picked up during his travels in Peru or Vietnam. No luck so far. Probably because developing countries don't yet routinely genotype their native TB germs.

The World Health Organization hopes to change that so that in the shrinking world, health officials can track down a TB outbreak wherever it starts.

Richard Knox, NPR News.

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