The number of people estimated to be latently infected with TB - that is infected with TB, which has not yet manifested symptoms - is around 2 billion. That is 1 in 3 people on the planet are infected by the bacteria. The World Health Organization’s website notes that on average 5-10% of those infected with TB will develop active TB.

That number is terrifying, but a new analysis published in the BMJ, suggests that the assumption that latent TB often has a very long incubation period of many years may be wrong - and that may change how we calculate the number of people affected, and our whole approach to tackling the disease.

This podcast features Lalita Ramakrishnan, professor of immunology and infectious diseases at Cambridge University, Paul Edelstein, professor of pathology and laboratory medicine at the University of Pennsylvania, and Marcel Behr, professor of medicine at McGill university.