A virulent group of TB germs spread from East Asia in waves propelled by industrialisation, World War I and Soviet collapse to yield some of the drug-resistant strains plaguing the world today, a study shows.
Researchers' massive trawl through nearly 5000 TB samples from 99 countries pinpointed changes in the DNA code to draw a partial family tree of the germ Mycobacterium tuberculosis.
A branch of that tree known as the "Beijing lineage" begins in a region around northeast China, Korea and Japan some 6600 years ago, said a study published in the journal Nature Genetics.
It evolved into several sub-lineages and strains, spreading eastward to Micronesia and Polynesia and westward to central Asia, Russia and eastern Europe.
The migration waves have become more pronounced over the past two centuries, spurred by industrialisation and urbanisation, as well as episodes of widespread deprivation like World War I that brought infected and vulnerable people close together.
Among the toughest modern-day versions - two multi-drug resistant (MDR) clones, started spreading through eastern Europe and Asia on an epidemic scale about 20-30 years ago, "coinciding with the collapse of the public health system of the former Soviet Union," said study co-author Thierry Wirth of France's National History Museum.
There was a single decrease visible on a chart plotting the global spread of the "Beijing lineage" from the year 1500 to 2000.
It coincided with a rise in antibiotic use in the 1960s and ended with the HIV epidemic from the 1980s.
TB itself is theorised to be about 40,000 years old.
Unravelling the disease's genetic history may offer pointers for tackling its spread.
MDR strains, which do not respond to frontline antibiotics, are a major concern as they are much more costly and difficult to treat.
In 2013, there were nine million new cases of TB and 1.5 million deaths worldwide, including 360,000 people who were also infected with HIV, the World Health Organisation said in its latest TB report.
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