In the United States, TB is much less common than it used to be. Of the some 13,000 new cases of active disease each year in the United States, over half occur in persons born outside of the country. Tuberculosis is very common in the developing world. It has been estimated that as much as a third of the world's population is infected with M. tuberculosis, and worldwide about 1.6 million people die of TB every year. TB and HIV are closely associated; people with HIV are much more likely to develop active disease if they are infected with the bacteria that cause TB.