Scientists have reconstructed ancient pandemics to figure out pathogen strategy

Ancient bacteria mutated to be better at infecting ancient humans. At the same time, in an effort to infect as many as possible

more new bacterial hosts have reduced theirinfluence on a person. Scientists decided to explain why this happens. In addition, Associate Professor of Archeology Maciej Henneberg, PhD Tegan Lukas from Flinders University and PhD Cara Holloway-Q from Deakin University analyzed data from 70,000 ancient skeletons to learn more about the spread of ancient diseases. Scientists have used marks on the bones as hallmarks of infection. The study results were published in PLOS ONE.

“Pathogens can kill the human host orinvade it without causing death. This ensures their survival, reproduction and distribution. Tuberculosis, treponematosis and leprosy are common chronic infectious diseases in which the host does not die immediately, ”explains Professor Henneberg, a renowned anthropologist.

Recall that treponematoses are non-venereal infectious diseases caused by spirochetes, bacteria indistinguishable from the pale spirochete (Treponema pallidum), which causes syphilis.

These are chronic infections such as endemic syphilis, yaws and pinta, which are found in specific geographic areas.

All three diseases - tuberculosis, treponematosis, and leprosy - are considered prime examples of the co-evolution of pathogens and human hosts. They span over 200 generations.

The prevalence of each of these threedisease decreases as a result of joint adaptation. It is a mutually beneficial process for the disease and the human host. In the last 5,000 years, before the advent of modern medicine, signs of tuberculosis on skeletons have become less common, and the incidence of leprosy in bones in Europe has decreased since the end of the Middle Ages. At the same time, signs of infection with treponematoses in North America decreased, especially in recent years before contact with the invading Europeans.

Research shows whether microbes become more transmissible, but less deadly, over time so that they can continue to spread.

From an evolutionary point of view, for a pathogen it hasmeaning to cause less harm to the owner, on which his survival depends. This is why high transmission levels decrease over time. An illustrative example is the mass infections of leprosy, tuberculosis and syphilis in the past, scientists explain.

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