US: TB hits lowest mark yet

The 2012 rate is down 6.1% from 2011 and is the 20th year in a row of falling incidence, according to provisional TB surveillance data reported to CDC's National Tuberculosis Surveillance System and published in the March 22 issue of Morbidity and Mortality Weekly Report.

Of 3,143 counties in the U.S., 1,388 – or 44.2% -- did not report a single new TB case during the period from 2010 through 2012, the agency said.

And even in the four states with the highest TB burden -- California, Texas, New York, and Florida – 136 of 441 counties (or 30.8%) did not report any new TB cases during that time frame.

The findings suggest that anti-TB programs are effectively preventing the disease, the CDC report said, noting that if rates had remained constant at the 1993 level, more than 200,000 additional cases would have occurred from 1993 through 2012.

The report comes 2 days before World TB Day on March 24, which commemorates the date in 1882 when German bacteriologist Robert Koch announced the discovery of the pathogen that causes TB, Mycobacterium tuberculosis.

But despite the falling numbers, the CDC report added, there remain important disparities: Foreign-born people have higher rates than U.S.-born citizens, and members of minority racial and ethnic groups have higher rates than whites.

Both the rate and number of TB cases among U.S.-born people fell in 2012, the CDC report said. There were 3,666 cases, down 8.2% from 2011, and the rate of 1.4 per 100,000 U.S.-born people was an 8.7% decline since 2011.

The same was true of foreign-born people, but both numbers and rates remained higher than among the U.S.-born population. There were 6,243 cases, down 4.1% compared with 2011, and the rate of 15.8 cases per 100,000 foreign-born people represented a decline of 8.6% decline since 2011.

Among whites in 2012, the rate of TB was 0.8 cases per 100,000, compared with 19.8 per 100,000 for Asians, 5.7 per 100,000 for blacks, and 5.2 per 100,000 for Hispanics.

Put another way, the CDC report said, TB rates among Asians, Hispanics, and blacks were respectively 25, 6.6, and 7.3 times higher than the rate among whites.

The impact of TB varied markedly by state, ranging from 0.4 cases per 100,000 in West Virginia to 9 per 100,000 in Alaska. The median rate was 2.3 cases per 100,000.

The 2012 rates were lower than 2011 rates in 33 states and the District of Columbia but rose in 17 states, the CDC report said.

The big four -- California, Texas, New York, and Florida -- each reported more than 500 cases for a total of 4,967, which was 49.9% of all TB reported in 2012.

The agency cautioned that the study is based on provisional TB data provided by the 50 states and the District of Columbia and case rates are based on estimated population numbers. Final numbers will be reported later this year.

The study was supported by the CDC. Authors are employees of the agency.

Primary source: Morbidity and Mortality Weekly Report
Source reference:
Centers for Disease Control and Prevention "Trends in Tuberculosis -- United States, 2012" MMWR 2013; 62: 201-205.

Source: MedPage Today