U.S. cases of tuberculosis fell 6.4 percent in 2011 to an all-time low, but missed a national target of eliminating the disease as cases among foreign-born individuals persisted, health officials said on Thursday.
Unless factors change significantly, the United States will not be able to eliminate TB - meaning fewer than one case per one million people - until the year 2100, according to the U.S. Centers for Disease Control and Prevention.
"Addressing the increasing difference between TB rates in foreign-born and U.S.-born persons is critical for TB elimination," the CDC said in its weekly report on death and disease, which was released ahead of World TB Day on March 24.
Overall, U.S. TB rates last year fell to 10,521 reported cases, or 3.4 cases per 100,000 people, the lowest level since national reporting began in 1953, the CDC said.
Despite these gains, the airborne infection is proving difficult to tame in some populations, especially among foreign-born individuals, blacks, Asians and people infected with HIV.
TB rates were 12 times higher among people born outside the United States. Of these infected individuals, more than half of the cases originated in just five countries: Mexico, the Philippines, Vietnam, India, and China, the CDC said.
Compared with whites, TB rates were seven times higher for Hispanics, eight times higher for blacks and 25 times higher for Asians last year.
Four states - California, Texas, New York and Florida - account for nearly half of all TB cases in the United States, according to the report.
TB is caused by the Mycobacterium tuberculosis bacteria. It can be cured with antibiotics but they must be taken daily for months to be effective. Because people do not always take the drugs as directed, multiple drug-resistant strains have emerged.
Cases of TB that are resistant to at least two common treatments, known as multidrug-resistant TB, accounted for 109 of all U.S. TB cases in 2010, the most recent year for which there are data. Foreign-born individuals accounted for 90 of these cases.
There were 4 cases of extensively drug-resistant TB - an infection that resists the most highly effective drugs - reported in the United States in 2010, all among foreign-born people.
The World Health Organization estimates that a third of the world's population is infected with the bacteria that cause TB. Last year, TB made nearly 9 million people sick and killed some 1.45 million people, according to WHO.
