Long before the Black Death killed millions across Europe in the Middle Ages, an earlier, more elusive version of the plague spread across much of Eurasia.

For years, scientists were unsure how the ancient disease managed to spread so widely during the Bronze Age, which lasted from roughly 3300 to 1200 B.C., and stick around for nearly 2,000 years, especially since it wasn’t spread by fleas like later plagues. Now, researchers say a surprising clue may help explain it, a domesticated sheep that lived more than 4,000 years ago.

Researchers found DNA from the plague bacterium Yersinia pestis in the tooth of a Bronze Age sheep discovered in what is now southern Russia, according to a study recently published in the journal Cell. It is the first known evidence that the ancient plague infected animals, not just people, and offers a missing clue about how the disease spread.

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“It was alarm bells for my team,” study co-author Taylor Hermes, a University of Arkansas archaeologist who studies ancient livestock and disease spread, said in a statement. “This was the first time we had recovered the genome from Yersinia pestis in a non-human sample.”

And it was a lucky discovery, according to the researchers.

“When we test livestock DNA in ancient samples, we get a complex genetic soup of contamination,” Hermes said. “This is a large barrier … but it also gives us an opportunity to look for pathogens that infected herds and their handlers.”

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The highly technical and time-consuming work requires researchers to separate tiny, damaged fragments of ancient DNA from contamination left by soil, microbes and even modern humans. The DNA they recover from ancient animals is often broken into tiny pieces sometimes just 50 “letters” long, compared to a full human DNA strand, which contains more than 3 billion of those letters.

Animal remains are especially tough to study because they are often poorly preserved compared to human remains that were carefully buried, the researchers noted.

The finding sheds light on how the plague likely spread through close contact between people, livestock and wild animals as Bronze Age societies began keeping larger herds and traveling farther with horses. The Bronze Age saw more widespread use of bronze tools, large-scale animal herding and increased travel, conditions that may have made it easier for diseases to move between animals and humans.

When the plague returned in the Middle Ages during the 1300s, known as the Black Death, it killed an estimated one-third of Europe’s population.

“It had to be more than people moving,” Hermes said. “Our plague sheep gave us a breakthrough. We now see it as a dynamic between people, livestock and some still unidentified ‘natural reservoir’ for it.”

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Researchers believe sheep likely picked up the bacteria from another animal, like rodents or migratory birds, that carried it without getting sick and then passed it to humans. They say the findings highlight how many deadly diseases begin in animals and jump to humans, a risk that continues today as people move into new environments and interact more closely with wildlife and livestock.

“It’s important to have a greater respect for the forces of nature,” Hermes said.

The study is based on a single ancient sheep genome, which limits how much scientists can conclude, they noted, and more samples are needed to fully understand the spread.

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The researchers plan to study more ancient human and animal remains from the region to determine how widespread the plague was and which species may have played a role in spreading it. 

They also hope to identify the wild animal that originally carried the bacteria and better understand how human movement and livestock herding helped the disease travel across vast distances, insights that could help them better anticipate how animal-borne diseases continue to emerge.

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The research was led by scientists at the Max Planck Institute for Infection Biology, with senior authors Felix M. Key of the Max Planck Institute for Infection Biology and Christina Warinner of Harvard University and the Max Planck Institute for Geoanthropology.

The research was supported by the Max Planck Society, which has also funded follow-up work in the region.

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Cases of gout are rising in younger individuals, according to a global study.

The condition, which is a type of inflammatory arthritis, steadily increased in people aged 15 to 39 between 1990 and 2021, researchers in China announced.

Although rates vary widely between countries, the total number of young people with the condition is expected to continue rising through 2035.

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The study, published in the journal Joint Bone Spine, investigated 2021 data from the Global Burden of Disease (GBD), spanning 204 countries within the 30-year timeframe.

The data measured gout prevalence, incidence and years lived with disability, tracking global trends over time. The results showed a global increase across all three outcomes.

Prevalence and disability years increased by 66%, and incidence rose by 62%. In 2021, 15- to 39-year-olds accounted for nearly 14% of new gout cases globally, the study found.

Men from 35 to 39 years old and people in high-income regions had the highest burden, but high-income North America topped the list for highest rates.

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Men were also found to have lived more years with gout due to high BMI, while women tended to have the condition as a link to kidney dysfunction, the study noted.

The total number of cases is expected to increase globally due to population growth, but the study projected that rates per population would decrease.

The researchers noted that data quality, especially in low-income settings, could have posed a limitation to the broad GBD data.

What is gout?

Gout is a common form of arthritis involving sudden and severe attacks of pain, swelling, redness and tenderness in the joints, according to Mayo Clinic. It most often occurs in the big toe.

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The condition occurs when urate crystals accumulate in the joint. These form when there are high levels of uric acid in the blood, which the body produces when it breaks down a natural substance called purines.

A gout flare-up can happen at any time, often at night, causing the affected joint to feel hot, swollen, tender and sensitive to the touch.

Purines can also be found in certain foods, like red meat or organ meats like liver and some seafood, including anchovies, sardines, mussels, scallops, trout and tuna, according to the Mayo Clinic. Alcoholic drinks, especially beer, and drinks sweetened with fruit sugar can also lead to higher uric acid levels.

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Uric acid will typically dissolve in the blood and pass through the kidneys into urine, but when the body produces too much or too little uric acid, it can cause a build-up of urate crystals. These are described by the Mayo Clinic as sharp and needle-like, causing pain, inflammation and swelling in the joint or surrounding tissue.

Risk factors for gout include a diet rich in high-purine foods and being overweight, which causes the body to produce more uric acid and the kidneys to have trouble eliminating it.

Certain conditions like untreated high blood pressure, diabetes, obesity, metabolic syndrome and heart and kidney diseases can increase the risk of gout, as well as certain medications.

A family history of gout can also increase risk. Men are more likely to develop the condition, as women tend to have lower uric acid levels, although symptoms generally develop after menopause.

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Untreated gout can cause worsening pain and joint damage, experts caution. It may also lead to more severe conditions, such as recurrent gout, advanced gout and kidney stones.

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The Mayo Clinic advises patients to seek immediate medical care if a fever occurs or if a joint becomes hot and inflamed, which is a sign of infection. Certain anti-inflammatory medications can help treat gout flares and complications.

Fox News Digital reached out to the researchers for comment.