Fewer surveys, particularly country-wide or region-wide (indicated by connecting lines) were available from Africa. The available data suggest that the average annual decline in the annual risk of infection was somewhere between 1 and 5%.
It should be recalled that these surveys were done before HIV could have impacted on the risk of infection that would make it apparent in tuberculin skin test prevalence surveys usually conducted in children around age 10 years. There is emerging evidence that the risk of infection has begun to measurably increase in some countries (e.g., in Kenya).
