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Did Human Survivorship Improve Following The Black Death Epidemic?

May 8, 2014
Image Caption: The Yersinia pestis bacteria that causes the bubonic plague (known as the Black Death) Credit: Thinkstock.com

Lawrence LeBlond for redOrbit.com – Your Universe Online

Killing tens of millions of Europeans during the mid-1300s, the medieval Black Death plague was one of the worst disease outbreaks humans have ever faced. But as devastating as the disease was, it may have helped human survival over the course of many generations, according to new research from Sharon DeWitte, PhD, Assistant Professor of Anthropology and Biology at the University of South Carolina.

Previous studies have shown that the disease targeted the elderly, sick and stressed people – however, not much was known about the substantial changes in the population, like overall health and mortality, both before and after the occurrence of the plague. It was known, however, that standards of living improved – particularly diet – following the epidemic.

Publishing a new study in the journal PLOS ONE, Dewitte examined whether the deaths of frail people during the Black Death, combined with consequent rising standards of living, may have resulted in healthier populations in post-Black Death London.

Because most of the available data is in historical documentation, such as tax records, DeWitte relied on the samples of nearly 600 skeletons from several pre- and post-Black Death cemeteries throughout London. She analyzed the corpses’ ages and hence modeled age estimates, mortality hazards, and birth rate data for these samples.

DeWitte found that post-Black Death samples had a higher proportion of older adults, suggesting that survivorship improved following the epidemic. Also, the results of hazards analysis indicate that mortality risks were lower in the post-Black Death population than before the epidemic struck in 1347. The combined results paint a pretty good picture of enhanced survival and decreased mortality following the Black Death – which subsided around 1351 – as well as improved health in some age groups.

DeWitte acknowledged that other factors could also be at play to enhance these differences, like migration of people to London following the bubonic plague. As such, it is likely that the post-Black Death skeletons contained a mix of both native Londoners and immigrants. She also noted that migration to London was just as common in the pre-Black Death era, indicating earlier samples could be mixed as well.

Dewitte also acknowledged that, “because the devastation caused by the Black Death was mostly consistent across nearly all of Europe, any migrants to London would have consisted of Black Death survivors and their descendants to the same extent as London’s native population,” as cited by Medical News Today.

However, she suggested that her study highlights the power that infectious diseases may have in shaping population-wide patterns of health and demography over both the short- and long-term.

“It really does emphasize how dramatically the Black Death shaped the population,” DeWitte told BBC News. “The period I’m looking at after the Black Death, from about 200 hundred years after the epidemic. What I’m seeing in that time period is very clear positive changes in demography and health.”

Although general health might have been improving, the aftermath of the epidemic would have been “horrifying and devastating” for those who survived, she said. “Those improvements in health only occurred because of the death of huge numbers of people.”

“This study suggests that even in the face of major threats to health, such as repeated plague outbreaks, several generations of people who lived after the Black Death were healthier in general than people who lived before the epidemic,” concluded DeWitte.

The bacterium — Yersinia pestis — that caused the widely devastating Black Death epidemic has evolved and mutated over centuries, and is still an effective killing machine today.

According to the World Health Organization (WHO), the modern day disease is spread to humans by the bite of infected fleas or from the handling of infected rodents.

If the bacteria reaches the lungs, pneumonic plague soon sets in, which is then transmissible from person to person through infected droplets spread by coughing. Initial symptoms of bubonic plague appear within seven to 10 days after infection. If diagnosed early, it can be treated successfully with antibiotics. Once pneumonic plague sets in, however, it becomes one of the most deadly infectious diseases, often killing patients within 24 hours. Mortality rate depends on how soon treatment is started, and often the health and age of the patient.

Recent outbreaks have shown that the plague may reoccur in areas that have long remained silent.


Source: Lawrence LeBlond for redOrbit.com - Your Universe Online



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