https://www.scientificamerican.com/article/scientists-solve-a-deadly-tb-mystery/

In 2005 and 2006, 53 patients who checked into a rural South Africa hospital turned out to be infected with extensively drug-resistant tuberculosis (XDR TB). The bacterium proved impervious to antibiotics, ultimately killing 52 of the patients.

This outbreak in Tugela Ferry, KwaZulu-Natal province, was the largest ever reported for XDR TB—and the primary strain involved currently accounts for nearly 80 percent of such infections in the province. New research finally tells the full story of the deadly strain's origin. As reported last October in the Proceedings of the National Academy of Sciences USA, it in fact emerged 250 miles away, more than a decade before the first recorded case. The researchers behind the paper say the multidisciplinary tool set they used to find its origin could help identify other drug-resistant pathogens early, as they emerge, and stop them from spreading.