History repeats itself, right? Bioarcheologist Melandri Vlok is banking on that as she explores lessons possibly applicable to COVID-19 by examining infectious disease spread among villagers 4,000 years ago.
Vlok’s research focuses on skeletal remains from the Man Bac archeological site in Vietnam. Excavated in 2005 and 2007, the site has been a treasure trove of information for archaeologists since thanks to its role during the transition away from foraging to farming in Mainland Southeast Asia.
Although the remains have been studied thoroughly over the years, they had not been analyzed for evidence of infectious disease. When her supervisor and fellow bioarcheologist Hallie Buckley thought she saw what might be yaws in a photo of the remains, the two decided to investigate further. Yaws, caused by Treponema pallidum bacteria, the same species responsible for syphilis, is a childhood disease that causes highly infectious skin lesions. It is spread easily through touch and, in advanced cases, causes severe, irreversible bone disfigurement.
While yaws has been eradicated from much of the world, it is still prevalent in the Western Pacific where it infects about 30,000 people annually. A previous global attempt to completely eradicate the tropical disease failed in the 1950s, and a more recent attempt was—ironically—curtailed by the COVID-19 pandemic.
Examining remains from 70 individuals at Man Bac, Vlok and Buckley discovered seven people—two adults, two adolescents and three children—who shared similar skeletal patterns of bone lesions and disfigurements consistent with systemic disease. Multi-layered new and remodeled bone was seen in many of the arms and legs, as well as in facial regions.
While bone enlargement can be attributed to a variety of diseases and traumas, the researchers said the “widespread and non-uniform nature of the enlargements in the Man Bac cases are more consistent with that of a systemic infection than metabolic or traumatic etiologies.”
These two possible cases of yaws infection are the first to be detected as long as 4,000 years ago. The age is significant for multiple reasons, one being that it was right around the time farming was introduced to Southeast Asia, causing an unprecedented movement of people as one previously isolated population began to interact with a second.
Additionally, there is a documented increase in the number of infants and children in the community at that time—and yaws is primarily transmitted through young persons. Caring for the elderly and other social initiatives in Man Bac have also been documented, signifying ease of transmission.
Lastly, the evolution of a disease and the length of time it has existed within society is relevant when addressing and/or predicting eradication efforts.
“Archaeology like this is the only way to document how long a disease has been with us and been adapting to us. We understand with COVID-19 today how fantastic that disease is at adapting to humans, and Treponema has been with us for so much longer,” said Vlok. “This shows us what happens when we don't take action with these diseases. It's a lesson of what infectious diseases can do to a population if you let them spread widely. It highlights the need to intervene because sometimes these diseases are so good at adapting to us, at spreading between us."
Photo: The Man Bac site. Credit: University of Otago.