"HEALTH officials are paid to feel apprehensive. For some years they have feared that tuberculosis (TB), an ancient scourge tamed by modern drugs, might evolve into a new, indestructible state. New strains of mycobacterium tuberculosis have already emerged, some resistant to isoniazid and rifampicin, two of the best known treatments, and some resistant to additional injected drugs. The advent of completely resistant TB seemed inevitable. Now it may have arrived."