The annual risk of tuberculosis infection used as predictor of the future incidence of smear-positive cases.

It has been estimated that in underdeveloped countries every 1% annual risk of tuberculosis infection results in an incidence of 50 per 100,000 smear-positive cases. However, workers had theoretically speculated that the incidence would be about one-third less in countries with good medical facilities. I decided to test the latter theory in the city of Riyadh (capital of Saudi Arabia) which enjoys a high standard of living, easy access to medical facilities, and free treatment.

Tuberculin survey in the Eastern Province of Saudi Arabia.

We present the results of the Mantoux test (5 units tuberculin) survey in the Eastern Province of Saudi Arabia, which was conducted as part of a nationwide epidemiological survey of tuberculosis. A total of 1105 subjects were screened out of whom 630 gave a history of BCG vaccination in the past and 363 were BCG-negative. Among BCG-negative children aged 5-14 years, only 5% had a positive Mantoux, a rate lower than most Third World countries but higher than developed countries were under 2% of children are tuberculin reactors.