WASHINGTON (Reuters) - Tuberculosis is appearing in the United States at the lowest rate ever recorded, with foreign-born people accounting for a majority of the cases, the Centers for Disease Control and Prevention on Thursday.
It said 13,293 TB cases were reported in the United States in 2007, with the TB rate declining by 4.2 percent from 2006 to 4.4 cases per 100,000 people.
Nearly 60 percent of the cases were seen in people born in other countries, with more than half of them from four nations -- Mexico, the Philippines, India and Vietnam, the CDC said.
The TB rate among foreign-born people was 9.7 times higher than those born in the United States, the CDC said.
Nearly a third of the world's population is infected with the bacterium that causes TB, although active TB disease develops in only a fraction of these people.
TB has been on the retreat in the United States for decades. The first government report tracking overall TB cases was in 1953, with a rate of 52.6 per 100,000, which has not been exceeded since. The 2007 rate was the lowest on record.
Tuberculosis in the United States was in the spotlight last year when Atlanta resident Andrew Speaker triggered an international health scare by flying to and from Europe for his wedding and honeymoon with a difficult-to-treat form of TB. He was forcibly treated on his return and has been released.
Dr. Thomas Navin, a CDC epidemiologist who worked on the TB report, said there was a TB resurgence in the United States in the late 1980s and early 1990s closely linked to the AIDS epidemic. That resurgence peaked in 1992 with a rate of 10.4 TB cases per 100,000 people, Navin said.
"Since 1992, we've seen a steady improvement in the rates of TB in the United States but since 2000, we've documented the fact that the rate of decline has slowed," Navin said.
The average decline in the TB rate was 7.3 percent per year from 1993 to 2000 but 3.8 percent per year since then.
The most recent figures show 646 people died of TB in the United States in 2005, Navin said.
Among U.S.-born racial and ethnic groups, TB hit blacks the hardest. Their rate was nearly eight times that of whites.
TB and AIDS are closely intermingled worldwide. Of the 13,293 U.S. TB cases reported in 2007, HIV test results are known for 7,708 people. Among those, 11.3 percent also were infected with the AIDS virus, the CDC said.
TB hits developing regions the hardest. The World Health Organization reported on Monday that there were 9.2 million new cases of TB worldwide in 2006, the latest year for which global figures were available, and TB killed 1.7 million people. Africa had the highest TB rates while Asia had the most cases.
Worldwide, an increasing threat involves cases of TB in which the bacterium has become resistant to treatment with standard antibiotics, making it much more dangerous.
The WHO reported last month that 5 percent of TB cases worldwide -- about 500,000 people -- are infected with so-called multi-drug-resistant TB, or MDR-TB, resistant to at least the first-line TB drugs.
The CDC did not have 2007 figures for MDR-TB, but said there were 116 cases MDR-TB cases in 2006, accounting for 1.1 percent of all TB cases. The CDC said in 2006 there were four cases of extensively drug-resistant TB, or XDR-TB, the form hardest to treat, and based on preliminary data two in 2007.
Editing by Maggie Fox and Bill Trott