The number of tuberculosis cases in the United States rose last year for the first time in nearly a quarter-century, the Centers for Disease Control and Prevention reported Thursday.
Twenty-nine states and the District of Columbia each had more cases in 2015 than 2014, raising questions -- but no definitive answers -- about a possible resurgence of one of the world's deadliest diseases.
The overall increase was relatively small: 157 more cases, bringing the 2015 total to 9,563. Two-thirds of the total were among people born abroad, with Asians accounting for the most cases (3,007) and the highest rate (28.2 cases per 100,000 persons). By comparison, there were only .5 cases per 100,000 whites last year.
Tuberculosis is a serious airborne bacterial disease that primarily attacks the lungs. The active form is contagious, while people latently infected don't show symptoms and are not contagious. About 11 million Americas are believed to be in that latter category, according to the CDC's last estimate in 2000.
The disease is treatable with antibiotics, but the course can be long and complicated. Certain forms of the bacterium that causes TB are becoming impervious to the drugs designed to kill them, leading to the development of multidrug-resistant strains of infection.
More than half of cases reported in 2015 were clustered in four states — California, Florida, New York and Texas — which have one-third of the U.S. population.