TB Genotype and Case Notification Rates, Vietnam | CDC EID

EID Journal Home > Volume 15, Number 10–October 2009

Volume 15, Number 10–October 2009
Research
Mycobacterium tuberculosis Genotype and Case Notification Rates, Rural Vietnam, 2003–2006
Tran N. Buu, Mai N.T. Huyen, Nguyen N.T. Lan, Hoang T. Quy, Nguyen V. Hen, Matteo Zignol, Martien W. Borgdorff, Dick van Soolingen, and Frank G.J. Cobelens
Author affiliations: Pham Ngoc Thach Tuberculosis and Lung Disease Hospital, Ho Chi Minh City, Vietnam (T.N. Buu, M.N.T. Huyen, N.T.N. Lan, H.T. Quy); Tien Giang Provincial Tuberculosis and Lung Disease Hospital, My Tho, Vietnam (N.V. Hen); World Health Organization, Geneva, Switzerland (M. Zignol); KNCV Tuberculosis Foundation, The Hague, the Netherlands (M.W. Borgdorff, F.G.J. Cobelens); Academic Medical Centre, Amsterdam, the Netherlands (M.W. Borgdorff, F.G.J. Cobelens); and National Institute of Public Health and the Environment, Bilthoven, the Netherlands (D. van Soolingen)

Suggested citation for this article

Abstract
Tuberculosis case notification rates (CNRs) for young adults in Vietnam are increasing. To determine whether this finding could reflect emergence of Mycobacterium tuberculosis Beijing genotype, we studied all new sputum smear–positive pulmonary tuberculosis patients registered for treatment in 3 rural districts in Vietnam during 2003–2006. Beijing strain infections were more frequent in younger patients (15–24 years of age, 53%) than in older patients (31%; p<0.001). The increase in CNRs for youngest patients was larger for disease caused by the Beijing genotype than by other genotypes, but the difference was not significant. For patients 15–24 years of age, 85% of fluctuations in CNRs between years was caused by fluctuations in Beijing genotype infections compared with 53% and 23% in the groups 25–64 and >65 years of age, respectively (p<0.001). These findings suggest that young adults may be responsible for introducing Beijing strains into rural Vietnam.

One third of the world's population is infected with Mycobacterium tuberculosis, and ≈9 million tuberculosis (TB) cases were diagnosed worldwide in 2006 (1). Introduced in the early 1990s, the directly observed treatment, short-course (DOTS) strategy is an essential component of the Global Stop TB Strategy and regarded as a highly cost-effective method for controlling the TB epidemic (2). In addition, the DOTS strategy has resulted in decreased numbers of TB cases in Peru, parts of the People's Republic of China, India, and Indonesia (3–6) a few years after those countries met the goals of the World Health Organization (WHO), which are to detect >70% and cure >85% of smear-positive TB cases (7).

Conversely, the DOTS strategy has had a limited effect (no decrease in numbers of TB cases) in other regions, such as the former Soviet Union and sub-Saharan Africa (3,8). In Vietnam, TB case notification rates (CNRs) have not decreased since 1997 when the National TB Control Program reached WHO goals (1,9). This absence of a stable rate decrease reflects a decrease in TB CNRs among middle-age persons, primarily women, which is compensated for by an increase in CNRs in young adults, primarily men (10). Several explanations for this phenomenon have been proposed, including the emerging HIV epidemic (11), rapid urbanization (12), and emergence of the M. tuberculosis Beijing genotype (13). Studies worldwide indicated that the Beijing genotype is widespread and associated with drug resistance (14–20). In Vietnam, a study of isolates from patients located mainly in Ho Chi Minh City showed that the Beijing genotype accounted for 55% of the M. tuberculosis isolates and was associated with young age and drug resistance (21). Another study in Ho Chi Minh City found that this genotype was more frequent among patients with treatment failure or relapse (22). Therefore, emergence of the Beijing genotype, or a higher rate of recurrence of Beijing genotype cases, could explain part of the increase in TB rates among young adults. However, these studies were conducted in large urban areas where rapid urbanization and internal immigration may have confounded these associations. Therefore, we assessed, in a population-based study, the role of the Beijing genotype in the TB epidemic in a rural setting in Vietnam. We studied trends in CNRs of new smear-positive TB cases caused by specific genotypes over time by age and sex, and age-specific variations in genotype distribution over time.

abrir aquí para acceder al documento CDC completo del cual se reproduce un 5%:
TB Genotype and Case Notification Rates, Vietnam | CDC EID