US TB rate down, but elimination still distant

Mar 24, 2011 (CIDRAP News) – The incidence of tuberculosis (TB) in the United States dropped almost 4% last year to its lowest level since 1953, but the nation still fell well short of a long-standing goal of eliminating the disease by 2010, the Centers for Disease Control and Prevention (CDC) reported today.

Marking World TB Day, the CDC said the nation had 3.6 cases per 100,000 people last year, a 3.9% drop from 2009. This was the lowest level since national reporting began in 1953, and it was 65.2% below the most recent peak in the early 1990s.

However, the goal of TB elimination in the United States—defined as less than 0.1 case per 100,000—remains elusive, the CDC noted in Morbidity and Mortality Weekly Report (MMWR).

Last year's fall in TB incidence was much smaller than the 11.4% drop reported for 2009 and was in line with the average decline of 3.8% per year from 2000 to 2008. The CDC said the findings suggest that the big drop in 2009 was an "aberration" that was probably related to changing migration patterns.

The agency also reported persistent big disparities in TB rates between foreign-born and US-born Americans and between non-Hispanic whites and other groups.

The nation as a whole had 11,181 TB cases in 2010. US-born Americans accounted for 4,378 cases, or 39.5% of cases in persons of known national origin. The rate for this group was 1.6 cases per 100,000, which was 4.6% lower than in 2009 and 77.8% lower than in 1993.

The number of cases among foreign-born Americans last year was 6,707, or 60.5% of the total, the CDC said. This translated into 18.3 cases per 100,000—11 times higher than in the US-born. But it was 4.3% lower than in 2009 and 46.8% lower than in 1993.

Compared with the TB rate in non-Hispanic whites, the rates in Hispanics, non-Hispanic blacks, and Asians were, respectively, seven, eight, and 25 times as high, the CDC reported.

"Among US-born racial and ethnic groups, the greatest racial disparity in TB rates was for non-Hispanic blacks, whose rate was seven times greater than the rate for non-Hispanic whites," the report adds.

People with HIV continued to bear a sizable share of the TB burden. Among patients with a known HIV test result, 8.6% (611 of 7,090) were also infected with HIV, the CDC said.

Figures on multidrug-resistant TB (MDR TB) for 2010 were not available, but 113 cases were reported in 2009, the report says. So far, just one case of extensively drug-resistant TB has been reported for 2010.

The goal of eliminating TB by 2010 was set in 1989 by the Advisory Council for the Elimination of Tuberculosis in partnership with the CDC, the report notes. At that time, it says, planners underestimated the impact of the HIV/AIDS epidemic, which fueled the TB comeback of the early 1990s. Also underestimated was the effect of the global increase in TB on disease rates among foreign-born residents of the United States.

In another article in this week's MMWR, the CDC says an investigation has led to the conclusion that the very large decreases in TB case rates reported for Georgia and Pennsylvania for 2009 are probably real and not the result of underreporting.

Georgia's reported TB case rate fell 14.3% in 2009, while Pennsylvania's dropped 38.7%, the article says. Georgia health officials, concerned about possible underreporting, launched an investigation in collaboration with the CDC.

The probe turned up "no evidence of surveillance artifact, underreporting, or underdiagnosis substantial enough to account for the magnitude of the declines," the report says. The investigators found only two uncounted cases in Georgia and six in Pennsylvania.

The CDC said it remains possible that diagnostic delays resulting from poor access to healthcare were a factor in the big TB declines seen in the two states and nationally in 2009. But the provisional data for 2010 don't show a "compensatory increase" in the number of cases.

CDC. Trends in tuberculosis—United States, 2010. MMWR 2011 Mar 25;60(11):333-7 [Full text]

CDC. Assessment of declines in reported tuberculosis cases—Georgia and Pennsylvania, 2009. MMWR 2011 Mar 25;60(11):338-42 [Full text]

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