Ancient bond between humans and TB uncovered

Tuberculosis, a disease that has plagued humanity for thousands of years, has a fascinating history that mirrors our own migration patterns. According to a study by Professor Sarah Dunstan, the bacterium responsible for tuberculosis, Mycobacterium tuberculosis, has co-evolved with humans for at least 40,000 years.

The story begins with the first migration of small hunter-gatherer groups moving around the southern rim of the Indian Ocean. This was followed by a second migration, where groups moved north of the Himalayas, eventually spreading into Siberia, East Asia, and China. The first wave was primarily driven by hunter-gatherers, while the second wave was led by agriculturalists.

Professor Dunstan's study, presented at a conference on 'heterogeneity in hosts and pathogens of tuberculosis', highlights the genetic diversity and interactions of tuberculosis hosts and pathogens, with a particular focus on the region of India. The research shows that the spread of TB lineages, specifically Lineage 1 and Lineage 2, mirrored human migration patterns.

Lineage 2, which arose in Asia and is more transmissible, followed the pattern of those migrating north of the Himalayas. On the other hand, Lineage 1, which is less transmissible, seems to have adapted to spread less among early hunter-gatherer groups moving around the southern rim of the Indian Ocean.

As agricultural societies formed, Mycobacterium tuberculosis adapted to spread more easily due to larger city populations providing more hosts. This adaptation is supported by a model called the two-layer hypothesis, which suggests that Asia was populated in two major phases, with the first migration happening between 50,000 and 65,000 years ago, and the second migration around 45,000 years ago.

The study demonstrates the long history of human-TB co-evolution, where the bacteria's transmission patterns change based on the human groups it infects, influenced by their lifestyle and population dynamics. Professor Dunstan studied the Y chromosome data and how it relates to indigenous and non-indigenous populations across Asia.

The conference, which continues till February 12, offers opportunities for students to present their ideas in one-minute flash talks and posters on display. Over 200 visitors interacted with each other at the conference over themes related to drug-resistant tuberculosis, extra-pulmonary TB, and developments in TB diagnosis.

This research opens the door for studies on how humans and pathogens might have evolved together in this region. As we continue to understand the complex relationship between humans and tuberculosis, we are one step closer to controlling and eradicating this ancient disease.