Mycobacterium tuberculosis genotype and case notification rates, rural Vietnam, 2003-2006

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 >or=65 years of age, respectively (p<0.001). These findings suggest that young adults may be responsible for introducing Beijing strains into rural Vietnam.

Figure 1

Typical spacer patterns of the Mycobacterium tuberculosis spoligotypes most frequently isolated from patients with smear-positive pulmonary tuberculosis, Vietnam, 2003–2006. EAI5 and EAI4 are East African–Indian genotypes.

Figure 2

Trends in case notification rates for patients with new smear-positive tuberculosis, by sex, Vietnam, 1997–2006. The annual percentage changes were –4.3% for male patients, –7.7% for female patients, and –5.1% for all persons.

Figure 3

Trends in case notification rates for patients with new smear-positive tuberculosis, by age, Vietnam, 1997–2006. The annual percentage changes were +4.8% for persons 15–24 years of age, –3.3% for those 25–34 years of age, –6.1% for those 35–44 years of age, –6.5% for those 45–54 years of age, –11.5% for those 55–64 years of age, and –7.8% for those >65 years of age.

Figure 4

Average annual percentage changes in case notification rates for patients with new smear-positive tuberculosis by age and sex, for the Vietnam genotype (A) and the Beijing genotype (B), Vietnam, 2003–2006. Black columns, total; gray columns, male patients; white columns, female patients. Error bars indicate 95% confidence intervals.

Figure 5

Number of new smear-positive tuberculosis cases, by mycobacterial genotype and patient age, Vietnam, 2003–2006. A), All patients; B) patients 15–24 years of age; C) patients 25–64 years of age; D) patients >65 years of age. White columns, other genotypes; gray columns, Vietnam genotype; black columns, Beijing genotype.