Global Tuberculosis Report -- 2012.pdf

BOX 2.7Reducing the burden of TB disease: a success story from CambodiaFor the last two decades, Cambodia has been known to have one of the highest levels of TB burden (in terms of rates per 100 000population) in the world. TB control in Cambodia was reinstated in 1994 following decades of civil confl ict and economic hardship. TBservices were fi rst limited to provincial and district hospitals. Decentralization of TB control services to the health centre level was initiatedin the early 2000s, with nationwide expansion achieved in 2005, contributing to rapidly increasing case notifi cations (depicted with asolid black line in Figure B2.7.1).At the early stage of DOTS expansion to health centres, the National TB Programme decided to directly measure the burden of TB througha nationwide prevalence survey, completed in 2002. A total of 22 160 people aged ≥15 years participated in the survey, grouped in 42geographically determined clusters. The survey identifi ed 81 smear-positive TB cases (63% were symptomatic) and 190 smear-negativeculture-positive cases. After adjustment for unconfi rmed TB and forFIGURE B2.7.1Case notification and estimated incidence rates inCambodia, 1990–2011Rate per 100 000 population per year700600500400300200100Estimated incidence rateCase notification rate1990 1995 2000 2005 2010FIGURE B2.7.2Estimated TB prevalence (all forms) in Cambodia,1990–2011Rate per 100 000 population200015001000Survey 150% reduction target1990 1995 2000 2005 2010Survey 2childhood TB, the prevalence rate for all forms of TB was estimated at1511 (range 1244–1803) per 100 000 population, one of the highestprevalence rates observed in the world in recent history.A second nationally representative survey was conducted in 2011. Intotal, 39 680 people aged ≥15 years were sampled from 62 clusters.95 smear-positive TB cases (46% were symptomatic) and 218 smearnegativeculture-positive TB cases were identifi ed. After adjustmentfor unconfi rmed TB and for childhood TB, the prevalence rate for allforms of TB was estimated at 817 (range 690–954) per 100 000population, showing a statistically signifi cant reduction since the fi rstsurvey.Most bacteriologically-confi rmed prevalent cases did not reportsymptoms listed in the screening criteria. The proportion of peoplereporting TB symptoms listed in the screening criteria amongbacteriologically-confi rmed cases declined from 30% in 2002 to 22%in 2011. This highlights the need to revise criteria for TB screening inself-reporting patients, in favour of more sensitive criteria than thetraditional but insensitive criteria of a cough of ≥2weeks. There wasa signifi cant decline in prevalence rates for all age groups but thebiggest reduction was observed in younger age groups. The 2011survey also highlighted the need for more sensitive diagnostics thansputum smear microscopy.The repeat survey provides robust evidence of a decline in TBburden in Cambodia, following DOTS expansion in 2002 (FigureB2.7.2). Results indicate a 45% reduction in the prevalence ofbacteriologically-confi rmed cases since the fi rst national prevalencesurvey conducted in 2002, that is, over a period of only 9 years.The Cambodia results provide a major success story for TB control.28 GLOBAL TUBERCULOSIS REPORT 2012