U.S. researchers say smoking-related tuberculosis could kill as many as 40 million people by 2050.

The study published Tuesday in the British Medical Journal says smoking has been linked to an increased risk of tuberculosis — a contagious lung disease that makes breathing almost impossible.

It says many of the projected new cases will come in Africa, the eastern Mediterranean and Southeast Asia.

But the researchers say aggressive anti-smoking campaigns and control of cigarettes could prevent 27 million TB deaths by 2050.

The study was carried out by a team at the University of California.