Some of the drug-resistant tuberculosis (TB) bacteria have spread from East Asia in waves propelled by industrialization, World War I and Soviet collapse, according to a study published in the journal Nature Genetics. Researchers studied nearly 5,000 TB samples from 99 countries and pinpointed changes in the DNA code to draw a partial family tree of the germ Mycobacterium tuberculosis.
Researchers claim that a branch of that tree known as the 'Beijing lineage' begins in a region around northeast China, Korea and Japan some 6,600 years ago. Thereafter, 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, owing to industrialization and urbanization, as well as episodes of widespread deprivation like World War I that brought infected and vulnerable people close together.
Study co-author Thierry Wirth said, "Among the toughest modern-day versions, two multidrug 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."
TB is theorized to be about 40,000 years old. MDR strains, which do not respond to front-line antibiotics, are a major concern as they are costly and difficult to treat. Unraveling the disease's genetic history may offer pointers for tackling its spread.