Tuberculosis Originated in Humans; Not Animals: Research

An international team of researchers led by Swiss Tropical and Public Health Institute (Swiss TPH) revealed in the month of September 2013 that the origins of human tuberculosis traced back to the African hunter-gatherers who lived around 70000 years ago.

The study conducted by the international team of researchers suggested that the origin of Tuberculosis (TB) was not in the animals that lived around 10000 years ago, as it is believed commonly. It is important to note that TB is one of the deadliest infectious diseases of humans and it kills 50 percent of the individuals who are left untreated. In the developing countries, it is found that even today, TB leads to 1-2 million deaths. The major threat in fighting against the disease is multidrug-resistance.

The researchers have now identified about the origin in space and time of this disease. The researchers made use of the whole-genome sequencing of 259 Mycobacterium tuberculosis strains, which were collected from various parts of the world. These were used for determining the genetic pedigree of the deadly bugs. The comparison of the genome indicated that TB mycobacteria originated around 70000 years ago in Africa.

During the study, the researchers compared the genetic evolutionary trees of mycobacteria and humans alongside. The phylogenetic trees of humans and the TB bacteria had a lot of similarity. The evolutionary paths of TB a well as humans had a striking similarity.

The researchers explained that TB bacteria and humans did not emerge in same region of the world but they migrated outside Africa together. Both these, thereafter, expanded across the world. It was the migratory behaviour of modern humans, along with their lifestyle changes, that led to favourable conditions for TB. The researchers also explained that because of this, the diversity of tuberculosis bacteria enhanced remarkably when the expansion of human population took place.
 
Human expansion is also known as Neolithic Demographic Transition (NDT) period. This NDT is combined with the new human lifestyles which lived in the larger groups as well as village-like structures, which in turn would have created the conditions for human-to-human transmission of TB.

The results also pointed out towards the fact that it is unlikely that TB would have been communicated from the domesticated animals to the humans, like in the case of other infectious diseases.