Scientists discover that the plague evolved as it killed millions during the first recorded pandemic


Known as the Justinian plague named after Emperor Justinian I, the Y. pestis outbreak of 541 is the world’s first recorded pandemic that killed millions of people. And now scientists have discovered that the bacteria evolved as it ravaged Europe.

At some point in school, we have all learned about the Black Death that killed 75 to 200 million people across Europe, Northern Africa and the Middle East in the 1300s. If that sounds like a scary disease, that’s because it is and it comes in three forms with several symptoms, some more severe than others.

According to WebMD:

Plague is a serious bacterial infection caused by the bacteria Yersinia pestis. It is transmitted mostly through the bite of a rodent flea or contact with an infected animal. In rare cases, you can get it through droplets coughed or sneezed into the air.

The most common sign of bubonic plague is one or more swollen and painful lymph nodes, called buboes, that develop quickly. Patients with this form also can have a sudden onset of fever, headache, chills, and weakness.

Symptoms of the other two forms of plague may be less obvious. Septicemic plague also brings chills and weakness, and can cause fever, abdominal pain, and shock. In this form, the skin on fingers, toes, and the nose can turn black and die because blood can’t get to those extremities.

The disease is curable today, but people who lived in the 1300s were not so lucky, nor were people who lived during the Justinian era in 541 when the first plague pandemic swept through Europe and Central Asia and stuck around for 200 years.

How did it stick around and terrorize Europe for so long that it killed half of the population?

Scientists analyzed the remains of plague victims from the era to extract DNA from the dead Y. pestis cells and found that the strain evolved and adapted to survive in certain areas.

Max Planck Institute for the Science of Human History PhD student Marcel Keller, who co-authored the study, said in a statement:

“The retrieval of genomes that span a wide geographic and temporal scope gives us the opportunity to assess Y. pestis’ microdiversity present in Europe during the First Pandemic.”

The team sought to reconstruct the lineage of the plague strain, which has been thought to have been brought to Europe by the Huns. What they found suggests the strain came from Central Asia, and had been around for hundreds of years before the pandemic began.

“The lineage likely emerged in Central Asia several hundred years before the First Pandemic, but we interpret the current data as insufficient to resolve the origin of the Justinianic Plague as a human epidemic, before it was first reported in Egypt in 541 AD,” Keller said.

“However, the fact that all genomes belong to the same lineage is indicative of a persistence of plague in Europe or the Mediterranean basin over this time period, instead of multiple reintroductions.”

The study, published by the Proceedings of the National Academy of Sciences, explains in more detail, including putting to rest the idea that the Huns were to blame.

Based on available data, it has been suggested that the most parsimonious location for the divergence event that gave rise to the First Pandemic lineage is Central Asia (28). All published genomes of the branches 0.ANT1, 0.ANT2, and 0.ANT5 that frame the First Pandemic lineage in the phylogenetic tree were sampled in the autonomous Xingjiang region in northwestern China or in Kyrgyzstan (40, 46). In addition, an ancient second- to third-century Y. pestis genome from the Tian Shan mountains in Central Asia (28) branches off basal to all the First Pandemic genomes. The resulting claim that the Huns might have brought plague to Europe is, however, unsubstantiated due to the gap of more than three centuries before the onset of the First Pandemic.”

What’s even more interesting, or horrifying, is that the plague genome shows deletions in their genetic code, which signals a type of evolution.

Co-author Maria Spyrou of the Max Planck Institute for the Science of Human History said:

“This is a possible example of convergent evolution, meaning that these Y. pestis strains independently evolved similar characteristics. Such changes may reflect an adaptation to a distinct ecological niche in Western Eurasia where the plague was circulating during both pandemics.”

The plague wiped out so many people across the Mediterranean basin and in Europe that it interrupted the construction of many projects, including an unfinished basilica that can still be seen today in Greece.

 

Early Christian basilica in Greece that remains unfinished partly due to the effects of the Justinian plague. Image via Wikimedia.

The plague swept through Greece, Italy, Turkey, Germany, Spain, Austria and France. Even Justinian himself contracted the disease in Constantinople, although he survived. The researchers also found that the plague reached the British Isles.

Based on archaeological dating in combination with its rather basal position within the clade, this genome is likely related to the very first occurrence of plague in Britain suggested for 544, potentially introduced via sea communications with Brittany following the outbreak in central Gaul in 543.

The plague’s reign of terror would come to an end by 750, but an unrelated strain of the plague known as the Black Death would strike the continent again in the 14th century, resulting in a drop in population that would not recover for 200 years.

The team hopes by studying the Justinian plague, they can learn more about Y. pestis and pandemics in general to help prevent them.

“This study shows the potential of palaeogenomic research for understanding historical and modern pandemics by comparing genomes across millennia,” senior author of the study Johannes Krause says.

“With more extensive sampling of possible plague burials, we hope to contribute to the understanding of Y. pestis’ microevolution and its impact on humans during the course of past and present pandemics.”

We could certainly use such information as the threat of future pandemics looms over our own society, which is more interconnected than ever before. Such a pandemic today may not be contained to a single continent and the fringes of others, but be worldwide, representing a challenge to scientists and health professionals around the globe.

 

More on the Justinian plague and the Black Death from True Crime & Mysteries:


Featured Image: Wikimedia


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