The Bubonic Plague Is Older Than You Think

TL;DR

Bubonic plague (Y. pestis) dates back over 5,000 years, far predating the medieval Black Death, and still infects people today.

Key Points

• 1.Plague is at least 5,000 years old. In 2021, researchers found the oldest known Y. pestis case in a man from present-day Latvia who died of septicemic plague, likely from a rodent bite — millennia before the Black Death.
• 2.Early plague spread through livestock, not fleas. A 2025 study found LNBA-era plague DNA in a domesticated sheep from the Eurasian steppes; humans likely contracted it by handling and consuming infected animals before the flea-transmission gene (ymt) evolved around 3,000–3,700 years ago.
• 3.The first plague pandemic struck in 541 CE. The Plague of Justinian killed 25–100 million people; 2025 DNA analysis of teeth from a mass grave in Jordan confirmed it was definitively Y. pestis, and the strain triggered ~18 waves of outbreaks over two centuries.
• 4.The Black Death originated in Central Asia, not China. A 2022 ancient DNA study traced the 14th-century strain to Central Asia; the China origin story came from a medieval poet's fictional tale mistaken for history. The Black Death killed at least one-third of Europe's population.
• 5.Surviving the plague left a genetic legacy with a downside. Natural selection favored plague-resistant genes in European survivors, but some of those same protective variants are linked to increased prevalence of autoimmune disorders like Crohn's disease today.
• 6.Plague still exists and a fourth pandemic is a real risk. Y. pestis currently circulates in Madagascar, the DRC, and Peru; a person in Arizona died of pneumonic plague in July 2025. The bacteria persists in rodents, body lice, soil, and amoebas, and no widely affordable vaccine yet exists.