TB can lie dormant for decades before it strikes; almost a quarter of the globe – or 1.7 billion people – is affected by latent TB infection. People with latent TB infection have no symptoms, are not contagious and most of them don’t know they’re infected.
This population is at risk of developing TB disease at some point in their life. Without treatment, 5 to 10 percent of infected people—or between 85 to 170 million people—will develop TB disease.
Those who live with TB patients have a 25 times higher risk of progression from latent to active TB than the general population. And children up to five years age have the highest risk of progression from infection to TB disease.
Treatment for latent TB infection has been available since the 1960s, yet very few people who are eligible for TB preventive therapy are taking it. Current treatment options are long—with people required to take a pill daily for 6 to 36 months. Even among those who start treatment, many fail to complete the full course.