Tuberculosis - Epidemiology

Epidemiology

Roughly one-third of the world's population has been infected with M. tuberculosis, and new infections occur at a rate of one per second on a global scale. However, most infections with M. tuberculosis do not cause TB disease, and 90–95% of infections remain asymptomatic. In 2007, there were an estimated 13.7 million chronic active cases. In 2010, there were 8.8 million new cases of TB diagnosed, and 1.45 million deaths, most of these occurring in developing countries. Of these 1.45 million deaths, about 0.35 million occur in those coinfected with HIV.

Tuberculosis is the second most common cause of death from infectious disease (after those due to HIV/AIDS). The absolute number of tuberculosis cases ("prevalence") has been decreasing since 2005, while new cases ("incidence") have decreased since 2002. China has achieved particularly dramatic progress, with an approximate 80% reduction in its TB mortality rate between 1990 and 2010. Tuberculosis is more common in developing countries; about 80% of the population in many Asian and African countries test positive in tuberculin tests, while only 5–10% of the US population test positive. Hopes of totally controlling the disease have been dramatically dampened because of a number of factors, including the difficulty of developing an effective vaccine, the expensive and time-consuming diagnostic process, the necessity of many months of treatment, the increase in HIV-associated tuberculosis, and the emergence of drug-resistant cases in the 1980s.

In 2007, the country with the highest estimated incidence rate of TB was Swaziland, with 1,200 cases per 100,000 people. India had the largest total incidence, with an estimated 2.0 million new cases. In developed countries, tuberculosis is less common and is found mainly in urban areas. Rates per 100,000 people in different areas of the world where: globally 178, Africa 332, the Americas 36, Eastern Mediterranean 173, Europe 63, Southeast Asia 278, and Western Pacific 139 in 2010. In Canada and Australia, tuberculosis is many times more common among the aboriginal peoples, especially in remote areas. In the United States the Aborigines have a fivefold greater mortality from TB.

The incidence of TB varies with age. In Africa, it primarily affects adolescents and young adults. However, in countries where incidence rates have declined dramatically (such as the United States), TB is mainly a disease of older people and the immunocompromised.