Trend in the annual risk of tuberculous infection in Egypt, 1950-1996

OBJECTIVE: To determine the trend in the risk of tuberculous infection in n on-BCG vaccinated children in Egypt in the period 1950-1996, METHODS: in 1949-1952, a tuberculin survey was carried out in Egypt by the World Health Organization (WHO) covering 103 districts. In 1995-1997 a tube rculin survey was carried in 73 620 primary school children in grade one in the same districts, using international guidelines. The trend in tuberculo us infection was determined by comparing the prevalence of Mantoux reaction s of greater than or equal to 6 mm in the two surveys in subjects without a pparent BCG scar aged 6-7 years. For an estimate of current risk of infecti on the 17 mm cut-off point (number with 17 mm plus twice the number with gr eater than 17 mm) was used. RESULTS: In 1995-1997, 76% of children had a BCG scar. Infection prevalence estimates in 14 766 non-BCG-vaccinated children with a mean age of 6.7 yea rs were 11.9%, 4.1%, and 2.1% for the cut-off points 6 mm, 10 mm, and 17 mm , respectively. Decline in the risk of infection was estimated to be in the order of 50% over 45 years, or 1.5% per year. The geometric mean annual ri sk of infection in the 6.7 years before the survey was estimated at 0.32% ( 95% confidence interval 0.27-0.40%), For Egypt, the incidence of smear-posi tive tuberculosis was estimated at 16 per 100 000 population, giving a case detection rate of 85% (range 56-100%). CONCLUSION: This survey has shown that the size of the tuberculosis problem in Egypt is considerably smaller now than it was 45 years ago.