Although experts frequently assert that nearly 1.7 billion people carry dormant tuberculosis worldwide, that figure may be a “gross exaggeration” of the real threat, a recent study concludes.

The study, published last month in the journal BMJ, found that nearly everyone who falls seriously ill with TB does so within two years of getting infected. So-called latent infections only rarely become active, even in old age.

Researchers “have spent hundreds of millions of dollars chasing after latency, but the whole idea that a quarter of the world is infected with TB is based on a fundamental misunderstanding,” said Dr . Lalita Ramakrishnan, a tuberculosis expert at the University of Cambridge and one of the study’s authors.

The challenge to conventional wisdom comes at an opportune time. On Sept. 18, the World Health Organization issued its annual TB report, and on Sept. 26, the United Nations General Assembly will hold its first high-level meeting on the disease.