Global Tuberculosis Report -- 2012.pdf

CHAPTER 2The burden of disease caused by TBKEY FACTS AND MESSAGES There has been major progress in reducing TB cases anddeaths in the past two decades. The 2015 MDG target of halting and reversing TBincidence has been achieved, with TB incidence fallingglobally for several years and declining at a rate of 2.2%between 2010 and 2011. Globally, the TB mortality ratehas fallen by 41% since 1990 and the world is on trackto reach the global target of a 50% reduction by 2015. Mortality and incidence rates are falling in all of WHO’ssix regions and in most of the 22 HBCs that account forover 80% of the world’s TB cases. Cambodia provides an important new success story forTB control in a HBC: a national population-based surveycompleted in 2011 showed that TB prevalence hadfallen 45% since a baseline survey in 2002. Despite this encouraging progress, the global burdenof TB remains enormous. There were an estimated8.7 million incident cases of TB in 2011 (13%co-infected with HIV). There were also 1.4 milliondeaths from TB (990 000 deaths among HIV-negativeindividuals and 430 000 among people who wereHIV-positive). These deaths included 0.5 million amongwomen, making TB one of the top killers of womenworldwide. Geographically, the burden of TB is highest in Asia andAfrica. India and China combined have almost 40% ofthe world’s TB cases; the South-East Asia and WesternPacifi c Regions of which they are a part account for60%. The African Region has approximately one quarterof the world’s cases, and the highest rates of cases anddeaths relative to population. Globally, 3.7% of new cases and 20% of previouslytreated cases are estimated to have MDR-TB. Estimates of the burden of disease caused by TB arebeing continuously improved at country level, supportedby WHO’s Global Task Force on TB Impact Measurement.The burden of disease caused by TB can be measured interms of incidence (defined as the number of new andrelapse cases of TB arising in a given time period, usuallyone year), prevalence (defined as the number of cases ofTB at a given point in time) and mortality (defined as thenumber of deaths caused by TB in a given time period,usually one year).This chapter presents estimates of TB incidence,prevalence and mortality (absolute numbers and rates)between 1990 and 2011 and (for prevalence and mortality)forecasts up to 2015 (in sections 2.1–2.3). These dataare used to assess progress towards achieving the globaltargets for TB control set for 2015: that incidence shouldbe falling (MDG Target 6.c) and that prevalence anddeath rates should be halved by 2015 compared with 1990(Box 1.3 in Chapter 1). Key aspects of the methods usedto produce the estimates are provided at the beginning ofeach section. 1 Section 2.4 contains estimates of the numberof prevalent cases of multidrug-resistant TB (MDR-TB) in 2011, and estimates of the proportion of MDR-TBcases globally, regionally and in high TB-burden countries(HBCs). 2In response to increasing demand and global attention,this 2012 global report is the first to feature estimates ofthe number of TB cases and deaths among children andthe first to include estimates of TB mortality among womenthat include HIV-associated TB deaths. 3 The chapteralso puts the spotlight on Cambodia, which providesa new success story for TB control at country level. Anational survey in 2011 showed that TB prevalence hadfallen by 45% in the 9 years since a baseline survey in2002.There is uncertainty in all estimates of the burdenof disease caused by TB. Section 2.5 profiles efforts toimprove measurement of the burden of the disease underthe umbrella of the WHO Global Task Force on TB ImpactMeasurement. These include efforts to strengthen surveillanceof cases and deaths via notification and vitalregistration (VR) systems, and national surveys of theprevalence of TB disease in global focus countries.1A detailed description is provided in Annex 1.2Chapter 4 includes a much fuller discussion of the MDR-TBepidemic and the latest data on progress in the diagnosis andtreatment of MDR-TB.3In previous reports, estimates were restricted to the number ofTB deaths among women who were HIV-negative.8 GLOBAL TUBERCULOSIS REPORT 2012