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Diseases often leave direct or indirect imprints on the skeletal system, as in the case of osteoporosis, and sometimes, tuberculosis. While skeletal remains inform about the past, advance

tools, such as biotechnology, help map and study diseases of the past. Helen Donahue, from the University College London School of Life and Medical Sciences, explains the relevance of

studying ancient remains to modern medicine. “Paleopathology can provide evidence of the epidemiology and past geographical range of ancient infections,” she says. “It can also give insights

into the social context of past human infections. For example, leprosy is linked with rural populations and mud floors, whereas TB is linked to the density of population so it increases in

cities. This is seen as long ago as ancient Egypt,” she adds. Donahue has extensively researched the history of tuberculosis and leprosy. A recent work was a 2012 study published in the New

England Journal of Medicine. The study conducted on bodies found in a sealed crypt in Vac, Hungary. The bodies were buried between the late 18th century and early 19th century, and were

found to have been naturally mummified due to conditions prevalent in the crypt. A large percentage of the bodies were found to have been infected with tuberculosis and the samples obtained

were sufficiently intact to enable molecular fingerprinting of the strain of Mycobacterium tuberculosis (MTB). “We have found that several individuals were infected with more than one strain

of MTB, and one individual had three different strains,” she says. “They were all from modern lineage-4 (European) but can be distinguished from each other. Today, this pattern of infection

is found in sub-Saharan Africa and there was speculation that it may have been driven by HIV and/or the impact of antimicrobial therapy. Our data from the 18th century suggest that this

phenomenon arises whenever there is a high level of infection in the population,” she continues. In certain cases, the disease in question may not affect the same demographic as it did in

the past. A 2012 paper by Mauro Rubini from the University of Foggia, Italy, studied the case of childhood leprosy in two mummies excavated from the second-third century BC and 8th-10th

century BC, one of which yielded the DNA of Mycobacterium leprae. The study was published in the International Journal of Osteoarchaeology. While childhood leprosy is now a rare occurrence,

the study of the disease is nevertheless important due to a lack of historical literature on the subject. “These are real-time markers of genetic changes, thus enabling better understanding

of the evolution of human pathogens,” says Donahue. There have also been instances where DNA evidence from remains has been used to prove or verify theories about the history of a disease.

Kirsten Bos, physical anthropologist from Canada’s McMaster University used DNA obtained from a burial site in London to prove that the culprit behind the Black Death was Yersinia pestis,

the highly virulent bacterium responsible for bubonic plague. She thus silenced opposition to the theory from researchers who claimed that the medieval pandemic was caused by a virus similar

to Ebola, an idea that received some traction, thanks to the book published on the topic. Bos further proved that all modern strains of the disease had evolved from the strain responsible

for the Black Death. This information may be imperative in understanding a disease which has still not been completely eradicated. India’s last recorded plague outbreak occurred 20 years ago

in Surat, claiming numerous lives. Minor outbreaks are reported each year all over the world, including a major one in the Democratic Republic of Congo in 2006, indicating the continuing

need for further study of the disease’s history to truly understand its propagation dynamics. Studying these diseases may even give us clues about human history. Studying obligate pathogens,

such as M leprae that have co-evolved with their hosts, may provide information about human migration across continents.