To estimate the risk and prevalence of Mycobacterium
tuberculosis (MTB) infection and tuberculosis (TB) incidence, prevalence,
and mortality, including disease attributable to human immunodeficiency virus
(HIV), for 212 countries in 1997.
A panel of 86 TB experts and epidemiologists from more than 40 countries
was chosen by the World Health Organization (WHO), with final agreement being
reached between country experts and WHO staff.
Incidence of TB and mortality in each country was determined by (1)
case notification to the WHO, (2) annual risk of infection data from tuberculin
surveys, and (3) data on prevalence of smear-positive pulmonary disease from
prevalence surveys. Estimates derived from relatively poor data were strongly
influenced by panel member opinion. Objective estimates were derived from
high-quality data collected recently by approved procedures.
Agreement was reached by (1) participants reviewing methods and data
and making provisional estimates in closed workshops held at WHO's 6 regional
offices, (2) principal authors refining estimates using standard methods and
all available data, and (3) country experts reviewing and adjusting these
estimates and reaching final agreement with WHO staff.
In 1997, new cases of TB totaled an estimated 7.96 million (range, 6.3
million–11.1 million), including 3.52 million (2.8 million–4.9
million) cases (44%) of infectious pulmonary disease (smear-positive), and
there were 16.2 million (12.1 million–22.5 million) existing cases of
disease. An estimated 1.87 million (1.4 million–2.8 million) people
died of TB and the global case fatality rate was 23% but exceeded 50% in some
African countries with high HIV rates. Global prevalence of MTB infection
was 32% (1.86 billion people). Eighty percent of all incident TB cases were
found in 22 countries, with more than half the cases occurring in 5 Southeast
Asian countries. Nine of 10 countries with the highest incidence rates per
capita were in Africa. Prevalence of MTB/HIV coinfection worldwide was 0.18%
and 640,000 incident TB cases (8%) had HIV infection. The global burden of
tuberculosis remains enormous, mainly because of poor control in Southeast
Asia, sub-Saharan Africa, and eastern Europe, and because of high rates of M tuberculosis and HIV coinfection in some African countries.