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To prevent TB spread, vigilance is necessary
A 'challenge to TB control in the United States'
A review of evaluable multidrug-resistant tuberculosis (MDR-TB) cases that occurred in the United States from 1993 to 2006 found that 49 (3%) met the definition for extensively drug-resistant XDR-TB cases. Of those, 17 (35%) were reported during 2000-2006, the Centers for Disease Control and Prevention reports.1
Though the case count is low, it should be considered a "minimum estimate," the CDC emphasized. In addition, the epidemiology of drug resistant TB appears to be changing. Compared with 1993-1999, cases from 2000-2006 were more likely to be in people who were foreign-born and less likely to be in people with HIV infection." XDR-TB presents a global threat and a challenge to TB- control activities in the United States," the CDC stated in reporting the data. "To prevent the spread of XDR-TB, renewed vigilance is needed through drug-susceptibility testing, case reporting, specialized care, infection control, and expanded capacity for outbreak detection and response.
The 49 XDR-TB cases were reported from nine states and one city, with the largest numbers in New York City (19 cases) and California (11 cases). HIV status was known for 29 (59%) of the 49 people with XDR-TB; 16 (55%) were HIV-positive. During 1993-1999, a total of 19 people with XDR-TB had known HIV status, of whom 14 (74%) were HIV-positive; during 2000-2006, 10 people had known HIV status, of whom two (20%) were HIV-positive.
Mortality in XDR-TB cases strongly was associated with HIV infection. Among 41 people with XDR-TB and known outcomes, 12 (29%) people died; 10 of those had HIV infection, and the other two did not have HIV test results reported.
In terms of drug-susceptible TB, a total of 13,767 TB cases were reported in the United States in 2006, down from 14,085 cases in 2005. The 2006 national TB case rate — 4.6 cases per 100,000 people — was the lowest since reporting began in 1953. However, the decline of 3.2 % in the national TB case rate from 2005 to 2006 was one of the smallest in more than a decade. Overall, the average annual decline in the national TB rate slowed from 7.3% per year in the period 1993-2000 to 3.8% per year in the period 2000-2006. People living with TB also continue to be severely affected by HIV. Among TB cases with a documented HIV test result, 12.4% were HIV-infected.
"Tuberculosis continues to have a significant and unacceptable impact on minorities and immigrant communities in the United States," says Kevin Fenton, MD, director of HIV, STD and TB Prevention at the CDC. "Blacks and Hispanics have tuberculosis rates that are about eight times higher than that of whites, and the rate for Asians is more than 21 times that of whites. Foreign-born individuals living in the United States have nearly 10 times the rate of TB as those born in the United States."