The nation's TB rate dropped more than 11 percent last year, the largest single-year decrease in more than 50 years of federal record keeping, the Centers for Disease Control and Prevention reported this week. TB rates have been falling, but generally about 4 percent a year.
The drop was so steep that some experts are cautious about celebrating. While testing overseas may explain the decline, underdiagnosis and undertreatment could also be factors, the CDC said. A final report is due in the fall.
"This is provisional data and still needs to be scrutinized," said Dr. Michael Leonard, an Emory University infectious diseases specialist.
Screening changes made in 2007 call for more complete testing of prospective immigrants suspected of having TB. They also require screening of children younger than 15, who previously were not tested.
If TB is diagnosed, the changes ensure that immigrants receive at least six months of treatment and are no longer infectious before coming to the United States.
The CDC is trying to analyze immigrant infections before and after the 2007 changes.
Tuberculosis is caused by bacteria that usually attack the lungs, and is spread through the air when an infectious person coughs or sneezes. If not treated properly, TB can be fatal.
It once was a major cause of death and illness, and in the late 1800s killed one out of every seven people living in the United States and Europe. But the development of antibiotics and public health efforts succeeded in treating infections and tracking down those they infected.
Last year, 11,540 U.S. cases were reported, down from 12,904 the year before. About 60 percent of the cases were immigrants, legal and illegal. About half were from just four countries
- Mexico, the Philippines, India and Vietnam. Cases from those countries have been falling.
