7 Deadly Epidemics You Didn’t Know Existed
•March 9, 2026
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Why It Matters
Revealing forgotten epidemics sharpens our understanding of disease dynamics and underscores the importance of proactive, equitable health monitoring to prevent the next global crisis.
Key Takeaways
- •Ancient East Asian coronavirus epidemic detected via genomic signatures 25,000 years ago
- •6th‑century Welsh Yellow Plague likely relapsing fever, spurred migration
- •735 Japanese smallpox outbreak killed one‑third, reshaped public health practices
- •1510 influenza pandemic preceded 1918 flu, spread via Afro‑Eurasian trade
- •Valley Fever epidemic in WWII California highlighted uneven disease screening
Summary
The SciShow video delves into seven obscure epidemics that have shaped human history, beginning with a primer on the distinction between epidemics and pandemics. It then journeys from a 23,000‑year‑old coronavirus outbreak in East Asia—identified through adaptive changes in virus‑interacting proteins across 2,500 modern genomes—to the 6th‑century Welsh Yellow Plague, likely caused by relapsing‑fever bacteria and linked to mythic yellow monsters and mass migration to Brittany. Key insights include the devastating 735 Japanese smallpox epidemic that claimed roughly a third of the population, disproportionately killing children, and the 1510 influenza pandemic that pre‑dated the famed 1918 flu, spreading along Afro‑Eurasian trade routes. The video also examines the mysterious 16th‑century Mexican cocoliztli, with recent DNA work suggesting Salmonella paratyphi C, and the World War II Valley Fever outbreak in California’s dust‑laden San Joaquin Valley, where systematic skin‑testing cut infection rates by half. Notable details feature a 2021 genetic study pinpointing coronavirus‑related protein evolution, the legend of y Fad Felen foretelling a king’s death, Japanese cultural practices of celebrating child recovery, and the military’s proactive screening that contrasted with the under‑screened Japanese internment camps. These anecdotes illustrate how societies have responded to disease threats across centuries. The broader implication is clear: uncovering hidden epidemics through genomics, archaeology, and historical records enriches modern epidemiology, highlighting the need for equitable surveillance, early‑warning tools, and public‑health infrastructure to mitigate future pandemics.
Original Description
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From the non-bubonic plague that killed a Welsh king, to the deadliest pestilence in 16th century Mexico, to a pandemic we're currently in the middle of (No, it's not coronavirus), here are 7 disease outbreaks spanning roughly 25,000 years of human history that you probably haven't heard of.
Hosted by: Hank Green (he/him)
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