A global killer’s origins may have been traced back to India. Mycobacterium tuberculosis, the bacterium that causes TB, has thrived in south Asia for millennia, but until now no one had studied the diversity of the strains present.
To do this, Niyaz Ahmed and his colleagues from the University of Hyderabad, India, analysed 91 samples of TB taken from all over the country, studying the number and type of short, repetitive DNA sequences within three key genes.
They discovered that the ancestral strain is widespread, suggesting that India is the ancient reservoir for TB, from which more recent strains evolved…
