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Measuring tuberculosis burden, trends, and the impact of control programmes
In countries where the incidence of tuberculosis is stable and HIV-1 absent, a control programme that reaches the WHO targets of 70%case detection and 85%cure would reduce the incidence rate by 11%(range 8-12) per year and the death rate by 12%(9-13) per year. If tuberculosis has been in decline for some years, the same case detection and cure rates would have a smaller effect on incidence. DOTS saves a greater proportion of deaths than cases, and this difference is bigger in the presence of HIV-1. HIV-1 epidemics cause an increase in tuberculosis incidence, but do not substantially reduce the preventable proportin of cases and deaths. Without greater effort to control tuberculosis, the annual incidence of the disease is expected to increase by 41%(21-61) between 1998 and 2020 (from 7·4 million to 10·6 million cases per year). Achievement of WHO targets by 2010 would prevent 23%(15-30) or 48 million cases by 2020.
The potential effect of chemotherapy (delivered as DOTS) on tuberculosis is greater in many developing countries now than it was in developed countries 50 years ago. To exploit this potential, case detection and cure rates urgently need to be improved in the main endemic areas.
What is the limit to case detection under the DOTS stra... Tuberculosis |
jrn_nsub.gif" alt="You are not entitled to access the full text of this document" title="You are not entitled to access the full text of this document" width=12 height=14"> What is the limit to case detection under the DOTS strategy for tuberculosis control? Tuberculosis, Volume 83, Issues 1-3, February 2003, Pages 35-43 Christopher Dye, Catherine J. Watt, Daniel M. Bleed, Brian G. Williams Abstract In year 2000, the WHO DOTS strategy for tuberculosis (TB) control had been adopted by 148 out of 212 countries, but only 27%of all estimated sputum smear-positive patients were notified under DOTS in that year. Here we investigate the way in which gains in case detection under DOTS were made up until 2000 in an attempt to anticipate future progress towards the global target of 70%case detection. The analysis draws on annual reports of DOTS geographical coverage and case notifications, and focuses on the 22 high-burden countries (HBCs) that account for about 80%of new TB cases arising globally each year. Our principal observation is that, as TB programmes in the 22 HBCs have expanded geographically, the fraction of the estimated number of sputum smear-positive cases detected within designated DOTS areas has remained constant at 40–50%although there are significant differences between countries. This fraction is about the same as the percentage of all smear-positive cases notified annually to WHO via public health systems worldwide. The implication is that, unless the DOTS strategy can reach beyond traditional public health reporting systems, or unless these systems can be improved, case detection will not rise much above 40%in the 22 HBCs, or in the world as a whole, even when the geographical coverage of DOTS is nominally 100%. We estimate that, under full DOTS coverage, three-quarters of the undetected smear-positive cases will be living in India, China, Indonesia, Nigeria, Bangladesh and Pakistan. But case detection could also remain low in countries with smaller populations: in year 2000, over half of all smear-positive TB cases were living in 49 countries that detected less than 40%of cases within DOTS areas. Substantial efforts are therefore needed (a) to develop new case finding and management methods to bridge the gap between current and target case detection, and (b) to improve the accuracy of national estimates of TB incidence, above all by reinforcing and expanding routine surveillance. Purchase PDF (116 K) |
The sixth Nationwide Tuberculosis Prevalence Survey in ... Tubercle and Lung Disease |
jrn_nsub.gif" alt="You are not entitled to access the full text of this document" title="You are not entitled to access the full text of this document" width=12 height=14"> The sixth Nationwide Tuberculosis Prevalence Survey in Korea, 1990 Tubercle and Lung Disease, Volume 74, Issue 5, October 1993, Pages 323-331 Y. P. Hong, S. J. Kim, D. W. Kwon, S. C. Chang, W. J. Lew, Y. C. Han Abstract Setting: Nationwide random sample survey for tuberculosis in 1990. Objective: To investigate the prevalence of tuberculosis infection, morbidity and drug resistance and BCG coverage, and to compare the findings with those of the previous 5 surveys. Design: The following investigations were performed: tuberculin test, BCG scar screening, chest miniature radiography (70 mm × 70 mm) for those aged over 5 years, sputum direct smear, culture and drug susceptibility test, and a questionnaire to obtain history of chemotherapy and symptoms. Results: The coverage of the investigation has been of more than 95%in each survey. The main findings are as follows: BCG coverage of those aged under 30 and of infants (aged under 1 year) has increased from 24%to 86%and from 1%to 79%respectively. The observed tuberculin positivity ( 10 mm in diameter) of subjects aged under 30 has decreased from 45%to 27%. The reduction of positivity was significant in children aged 5–9 years, from 34%to 8%. The annual risk of infection has dropped by over 6%annually. The prevalence of pulmonary tuberculosis per 100 000 has decreased: direct smear-positive from 690-143, smear and/or culture positive from 940-241 and active cases from 5065-1842 respectively. The drug resistance rate had increased to the peak of 47%in 1980, but had decreased to 27%in the last survey. Conclusion: The tuberculosis situation has improved significantly in every aspect in the last 25 years. RésuméCadre: Enquête nationale d'échantillons randomisés pour dépister la tuberculose en 1990.Objet: Evaluer la prévalence de l'infection tuberculeuse, la morbidité et la résistance aux drogues, ainsi que la couverture vaccinale par le BCG. Comparaison avec les 5 enquêtes précédentes. Schéma: Les investigations suivantes ont été faites: test tuberculinique, dépistage des cicatrices vaccinales, radiophotographie thoracique (70 mm × 70 mm) chez les sujets âgés de plus de 5 ans, examen bactériologique des crachats, culture et test de sensibilité aux drogues, questionnaire pour obtenir des détails sur les antécédents de chimiothérapie et les symptômes. Résultats: La couverture de l'investigation a dépassé 95%pour chaque enquête. Les principales constatations sont les suivantes: la couverture vaccinale des sujets âgés de moins de 30 ans et des nouveaux-nés (âgés de moins d'un an) a augmenté de 24%à 86%et de 1%à 79%respectivement. La positivité tuberculinique observée ( 10 mm de diamètre) chez les sujets âgés de moíns de 30 ans a diminué de 45%à 27%. La diminution de la positivité était significative chez les enfants âgés de 5 à 9 ans, passant de 34%à 8%. Le risque annuel d'infection a diminué de 6%par an. La prévalence de la tuberculose pulmonaire pour 100 000 habitants a diminué : pour les positifs à l'examen direct de 690 à 143, pour les frottis positifs et/ou les positifs à la culture de 940 à 214, et les cas actifs sont passés de 5065 à 1842. Le taux d'antibiorésistance avait augmentéà un pic de 47%en 1980, alors que lors de la dernière enquête il s'était abaissé à 27%. Conclusion: La situation de la tuberculose s'est améliorée de façon significative dans tous ses aspects depuis 25 ans. Purchase PDF (1118 K) |
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Measuring tuberculosis burden, trends, and the impact of control programmes