U.S. Tuberculosis Cases at All-Time Low; Drug Resistance Remains a Threat
Tuberculosis rates in the United States reached an all-time low in 2006, though progress to eliminate TB continued to slow. Drug-resistant TB, including extensively drug-resistant TB, presents significant challenges to treatment and control of the disease in the United States and abroad, according to articles in today’s Morbidity and Mortality Weekly Report (MMWR).
“Tuberculosis continues to have a significant and unacceptable impact on minorities and immigrant communities in the United States,” said Dr. Kevin Fenton, director of CDC’s National Center for HIV, STD and TB Prevention. “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.”
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 persons – was the lowest since reporting began in 1953. However, the decline of 3.2 percent 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 percent per year in the period 1993-2000 to 3.8 percent per year in the period 2000-2006.
Persons living with TB also continue to be severely impacted by HIV. Among TB cases with a documented HIV test result, 12.4 percent were HIV-infected.
Multidrug resistant TB (MDR TB) is TB that is resistant to at least two first line therapies – isoniazid and rifampin. Extensively drug-resistant TB (XDR TB) is TB resistant to at least isoniazid and rifampin among the first-line anti-TB drugs and among second-line drugs, is resistant to any fluoroquinolone and at least one of three injectable drugs. Drug-resistant TB is difficult and costly to treat and can be fatal.
“Tuberculosis that is resistant to many of the standard drugs used to treat the disease challenges our ability to treat and control TB,” Dr. Fenton said. “In the United States, we have made great progress since the early 1990s against TB that is resistant to multiple first line treatments and had seen declines in these cases. Recently however, our success against MDR TB has slowed.”
XDR TB renders patients virtually untreatable with available drugs, particularly those in areas with less access to the full range of effective drugs. CDC’s new analysis, which includes provisional data for 2006, found that between 1993 and 2006, there were 49 XDR TB cases in the United States reported to the CDC.
XDR TB continues to be widely distributed geographically in the United States and abroad, causing public health concern. The risk of XDR TB appears to be low in the United States. However, due to the ease with which TB can spread, XDR TB will continue to pose a serious risk to the United States as long as it exists anywhere else in the world.
“CDC and its domestic and international partners are taking many steps to prevent further spread of drug-resistant TB and to reduce the overall burden of the disease,” said Dr. Ken Castro, director of CDC’s Division of Tuberculosis Elimination. “These efforts include developing new treatment regimens, increasing the capacity of health professionals to provide effective treatment, and issuing new recommendations for improved screening and treatment for U.S. immigrants.”
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