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

OBJECTIVE
To determine the trend in the risk of tuberculous infection in non-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 tuberculin survey was carried in 73 620 primary school children in grade one in the same districts, using international guidelines. The trend in tuberculous infection was determined by comparing the prevalence of Mantoux reactions of > or =6 mm in the two surveys in subjects without apparent BCG scar aged 6-7 years. For an estimate of current risk of infection the 17 mm cut-off point (number with 17 mm plus twice the number with greater 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 years 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 risk 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-positive tuberculosis was estimated at 16 per 100000 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.