Tuberculosis (TB) remains one of deadliest infectious diseases of humans, killing 50% of individuals when left untreated. Even today, TB causes 1-2 million deaths every year mainly in developing countries. Multidrug-resistance is a growing threat in the fight against the disease.
An international group of researchers led by Sebastien Gagneux from the Swiss Tropical and Public Health Institute (Swiss TPH) has now identified the origin in time and space of the disease. Using whole-genome sequencing of 259 Mycobacterium tuberculosis strains collected from different parts of the world, they determined the genetic pedigree of the deadly bugs. This genome comparison to be published September 1st in the journal Nature Genetics indicates that TB mycobacteria originated at least 70,000 years ago in Africa.
Stunningly close relationship between humans and M. tuberculosis
The researchers compared the genetic evolutionary trees of mycobacteria and humans side-by-side. And to the researcher's surprise, the phylogenetic trees of humans and the TB bacteria showed a very close match. "The evolutionary path of humans and the TB bacteria shows striking similarities," says Sebastien Gagneux.
This strongly points to a close relationship between the two, lasting tens of thousands of years. Humans and TB bacteria not only have emerged in the same region of the world, but have also migrated out of Africa together and expanded all over the globe.
The migratory behaviour of modern humans accompanied with changes in lifestyle has created favourable conditions for an increasingly deadly disease to evolve. "We see that the diversity of tuberculosis bacteria has increased markedly when human populations expanded," says evolutionary biologist Sebastien Gagneux.