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Chapter 1 : Global Burden of Tuberculosis
This chapter reviews the current epidemiology of tuberculosis (TB) in the world. Although the authors concentrate on the number of new cases of deaths from this disease, they also aim at presenting the exact numbers of new cases of TB and deaths from TB that occur each year. The ability of the tuberculin skin test to detect the presence of Mycobacterium tuberculosis infection can be used to measure the prevalence of infection. The annual risk of infection is the probability that any individual will be infected with M. tuberculosis in 1 year. It is estimated that about 1,700 million people are infected with M. tuberculosis. Primary resistance is defined as the presence of drug resistance to at least one anti-TB drug in a TB patient who has never received prior treatment. Without recognition of the TB crisis confronting the world and prompt, effective action, the TB epidemic can be expected to worsen for several reasons. First, demographic forces are at work. Children born in past decades in regions with high population growth rates are now reaching the ages at which morbidity and mortality for TB are high. Second, famine, war, and natural disasters that create large populations of displaced, malnourished people in crowded living conditions may cause increases in TB case rates. Third, age-specific TB incidence rates can be expected to rise in those areas of the world where immunity of the population is seriously challenged by HIV infection.