A Millennium of Tuberculosis

The origin and evolution of tuberculosis has been determined from the largest study of this disease.

Nowadays tuberculosis (TB) remains one of the deadliest infectious diseases worldwide, killing 1.7 million people worldwide in 2017. Despite the number of TB cases declining, one in four people globally are infected. Tuberculosis usually affects your lungs but in some cases can spread through the blood flow to your bones, kidney, brain and spine, and whilst this can take different forms, the most common form is called Lineage 4.

It's no secret that "coughs and sneezes spread diseases". TB is easily transmitted this way and individuals with weakened immune systems being particularly susceptible to contracting tuberculosis. Tuberculosis has been treated with antibiotics for the past 60 years but our control over this disease is threatened by emerging antibiotic resistance.

In order to resolve this public health challenge, we need to understand the origin of this disease, how it spread historically and how it changes form into antibiotic resistant strains. To tackle this, teams of researchers all over the world collected tissue samples obtained from a range of sources over different time periods; from mummies up to present day. “It is the most comprehensive data set to date,” said Professor Francois Balloux from University College London who was part of the team.

They analysed 1,700 samples of saliva, as well bone or soft tissue samples from 15 countries using a technique called genome sequencing, which investigates the genetic information locked up in these important samples. Based on the results of these tests, the researchers confirm that the origin of tuberculosis is dated back to Europe 1,000 years ago, with world-wide spread of tuberculosis linked to colonisation. In terms of antibiotic resistance, the study highlighted that the sub-categories resistant to treatment by antibiotics only spread locally after emergence. This was quite surprising but nevertheless a very important and promising finding. 

Addressing the spread of incurable versions of tuberculosis, Francois said he is “much more optimistic that local programs really are useful because they won’t be swamped by resistant strains from elsewhere.” Understanding how resistant strains have evolved and spread could eventually lead to development of new treatment, researchers hope, with a view to eradicating this deadly disease.