More than one-third of the global population is infected with the tuberculosis (TB ) bacterium, and TB disease remains one of the world’s leading causes of disease and death. Each year, 8 million people become ill with tunerculosis, and 2 million people die from the disease.

In the United States, the latest national surveillance data show a significant, but slowing, decline in the case rate of TB. In 2004, a total of 14,511 TB cases were reported in the U.S. The overall TB case rate – 4.9 per 100,000 persons – was the lowest rate ever recorded since reporting began in 1953. However, the decline in the case rate from 2003 to 2004 was one of the smallest in more than a decade ( 3.3 percent compared with an average of 6.8 percent per year ). Seven states now bear more than half the total burden of TB disease in the U.S. California, Florida, Georgia, Illinois, New Jersey, New York, and Texas account for 59.9% of the national case total. The toll continues to be greatest among minority and foreign-born individuals, who consistently have higher rates of TB disease.

TB’s racial and ethnic disparities

In 2004, minority populations had rates of tuberculosis significantly higher than the overall U.S. average. The 2004 TB case rate among Asians was 20 times higher than that among whites ( 26.9/100,000 and 1.3/100,000, respectively ), while blacks ( 11.1/100,000 ) and Hispanics ( 10.1/100,000 ) each had rates eight times higher than whites.

In 2004, for the first time, there were more cases of TB among Hispanics than any other ethnic group. However, the TB rate among Hispanics decreased slightly from 10.3 in 2003 to 10.1 in 2004. This divergent trend was the result of a 3.6 percent increase in the U.S. Hispanic population between 2003 and 2004.

Impact on foreign-born persons

The TB rate among foreign-born individuals ( 22.5/100,000 ) was nearly nine times the rate among persons born in the United States ( 2.6/100,000 ). Individuals born outside the United States accounted for more than half ( 7,701 cases, or 53.7 percent ) of all new TB cases in 2004.

While the TB rate among U.S-born persons has declined 64.6 percent over the past 12 years, the rate among foreign-born persons has declined only 33.9 percent.

Ninety-five percent of Asians reported to have TB in the U.S. in 2004 were foreign-born. Foreign-born individuals also accounted for the majority – 74 percent – of cases among Hispanics in the U.S. Globally, Asia accounts for the largest number of TB cases. The impact of TB on Mexico is also worrisome because many Hispanics diagnosed with TB in the U.S. were born in that country.

Accessing and completing TB therapy

Treatment is recommended for 6 to 9 months, and patients who do not complete therapy are at increased risk of developing multidrug-resistant TB ( MDR TB ). The most recent treatment-completion data ( 2001 ) show that 81.4 percent of U.S.-born and 80.4 percent of foreign-born TB patients completed therapy within one year. There was no significant variation in treatment completion by race.

Significant decline seen in multidrug resistant TB

Cases of MDR TB have declined sharply in the U.S. over the past decade. In 2003, the most recent year for which there is resistance rate reporting, 114 individuals were reported with MDR TB – a 76.5 percent decline since 1993. Of these individuals, 28 were born in the U.S. and 86 were born in other nations. Because previous data suggest little variation in rates of treatment completion by country of origin, the greater proportion of cases of MDR TB among foreign-born individuals is likely the result of TB infection in the person’s country of origin, where MDR TB rates are higher than in the U.S.

Source : CDC, 2005


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