NEW YORK, NY March 24, 2008 —City health officials say tuberculosis rates are down for the 15th straight year. But they are concerned about a persistent strain of the disease in Harlem and the Bronx. WNYC’s Fred Mogul has more.

In 2007, for the first time in several years, fewer than 1,000 city residents contracted the potentially-deadly-but-generally-treatable lung disease. Almost three-fourths of them were immigrants.

But in Harlem and the Bronx, a cluster of TB cases dating back to 2003 has confused local and national experts. This cluster mostly is not immigrants. According to a study of bacterial DNA, the cases are linked – but how the more than 40 people are connected to each other mostly isn’t clear.

The outbreak has become more concerning recently with the emergence of a multiple-drug-resistant version of the same strain in the same geographic area.

The city’s top TB official says the Health Department is expanding its investigation – and a public information campaign.

For WNYC, I’m Fred Mogul.