Ans. is 'a' i.e., 1% increase in AIR is equivalent to 70 new cases of TB Annual Infection Rate (also known as Tuberculin conversion index) o AIR is the % of population under study who will be newly infected by M. tuberculosis amongst the noninfected of the preceeding survey during the course of one year. o It reflects the annual risk of being infected (or reinfected) in a given community. o In other words, it expresses the attacking force of TB in a community. o It is considered one of the best indicator to evaluvate the TB problem and its trend. o In developing countries, every I% of of annual risk of infection is said to correspond to 50 new cases of smear positive pulmonary TB, per year for 1,00,000 general population. o The higher the rate the greater the problem. o Good treatment programme lowers the risk of TB infection in the community.