The decline of tuberculosis in Yemen: evaluation based on two nationwide tuberculin surveys.

SETTING

Yemen.

OBJECTIVE

To review the epidemiological situation of tuberculosis (TB) in Yemen by conducting a tuberculin survey and by comparing the results obtained with those of a previous tuberculin survey from 1991.

DESIGN

A nationwide tuberculin survey enrolling 31,276 schoolchildren aged between 7 and 12 years.

RESULTS

Skin indurations were recorded for 28,499 schoolchildren, of whom 16,927 (59.4%) had no bacille Calmette-Guérin (BCG) scar. Analysis of the distribution of indurations was difficult as it did not show any bimodal pattern. Prevalence of infection and annual risk of tuberculosis infection (ARTI) were thus estimated using the mirror image and mixture methods, and not the cut-off point method. The two methods indicated similar results: respectively 0.45% and 0.51% for prevalence of infection, and 0.05% and 0.05% for ARTI. In comparison with the 1991 tuberculin survey, the average annual decline of ARTI was 9.0% by the mirror method and 5.5% by the mixture method.

CONCLUSION

Yemen seems to have a low ARTI (0.05%), and TB infection seems to be declining considerably. Analysis of the survey results highlighted the limitations of tuberculin surveys in countries with comparable epidemiological situations.