The Trembling Death: Solving the Mystery of the 'Laughing Sickness' (Kuru)

[00:00:00]Deep in the impenetrable mist-shrouded highlands of Papua New Guinea, an isolated tribe known as the Fore people began to die.

[00:00:11]It started with a subtle tremor, a slight [music] instability in the step.

[00:00:16]But within months, the victims would lose complete control of their bodies.

[00:00:22]They would stumble, [music] sway, and shake so violently they could no longer sit upright.

[00:00:31]Then came the most terrifying [music] symptom of all.

[00:00:36]In the final stages of the disease, patients would often burst into uncontrollable manic fits of laughter.

[00:00:45]It wasn't laughter born of joy, but a cruel neurological [music] malfunction.

[00:00:50]The local Fore people called it kuru, which translates literally to trembling or shivering. [music] To the outside world, it became known by a more sinister name, the laughing [music] sickness.

[00:01:05]By the mid-1950s, this bizarre [music] affliction was wiping out entire villages, baffling the world's [music] top scientists, and threatening to push an entire civilization [music] to the brink of extinction.

[00:01:21]Today, we dive into one of the most chilling medical mysteries [music] of the 20th century, a disease so baffling that solving [music] it required rewriting the laws of biology.

[00:01:36]When Australian administrators and Western doctors first made contact with the Fore people in the 1950s, they realized they were looking at a demographic catastrophe.

[00:01:49]Kuru was a death sentence. Once symptoms started, mortality was 100%.

[00:01:57]There was no cure, no treatment, and no survivor.

[00:02:03]But, there was a bizarre pattern to the deaths that left doctors scratching their heads.

[00:02:11]The disease heavily targeted adult women and young children of both sexes.

[00:02:17]Adult men were almost entirely spared.

[00:02:21]Why? Enter Dr. Carleton Gajdusek, an American virologist and pediatrician, and Shirley Lindenbaum, an Australian anthropologist.

[00:02:32]They arrived in the Highlands determined to unmask the killer.

[00:02:37]Scientists first suspected a genetic disease, but the pattern didn't fit.

[00:02:43]Kuru spread too quickly and mostly affected women and children, not the men living in the same villages.

[00:02:52]If it wasn't in their DNA, it had to be environmental.

[00:02:58]Was it a toxin in the soil, a rare tropical virus, or something lurking in their diet?

[00:03:08]To solve the medical mystery, Shirley Lindenbaum had to look past the microscope and look closely at the culture of the Fore people.

[00:03:18]Specifically, how they treated their dead.

[00:03:23]Before the mid-20th century, when a member of the Fore tribe died, the community practiced a form of ritualistic funerary cannibalism.

[00:03:34]The Fore practiced ritual funerary cannibalism, believing consuming deceased relatives was a final act of love and respect.

[00:03:46]But, look at how the ritual was divided.

[00:03:50]The adult men, who were warriors believed consuming human flesh weakened them for battle, so they rarely participated. If they did, they only ate the choice muscular tissue.

[00:04:05]The women and children, however, were tasked with handling the bodies and consuming the rest, including the internal organs and crucially the brain.

[00:04:16]Women and children usually consumed the brain. Lindenbaum had a breakthrough.

[00:04:22]The transmission of Kuru perfectly matched the demographics of the funeral feast. The killer was inside the brain.

[00:04:32]By the late 1950s, colonial authorities banned the practice of cannibalism, and almost immediately new cases of Kuru began to plummet among children.

[00:04:44]The link was undeniable.

[00:04:47]But for Dr. Gajdusek and the medical community, solving the how only opened up an even bigger, more frustrating what.

[00:04:57]What exactly was living inside those brains?

[00:05:01]Gajdusek took brain samples from Kuru victims back to the United States.

[00:05:06]He injected them into chimpanzees.

[00:05:09]Years later, the chimps developed the exact same trembling symptoms. This proved Kuru was infectious. It could be caught. But here is where science broke down.

[00:05:22]When researchers tried to isolate the pathogen, they found nothing.

[00:05:27]Infectious diseases normally rely on bacteria or viruses carrying DNA or RNA.

[00:05:37]But researchers found neither.

[00:05:41]But whatever was causing Kuru was indestructible.

[00:05:46]Researchers exposed the samples to heat, radiation, and powerful chemicals, yet they remained infectious. And yet, when injected back into animals, the brains still became infected. How could something be alive, transmit a disease, and yet have no DNA?

[00:06:07]How could it survive punishments that would sterilize any known life form?

[00:06:14]The answer wouldn't be fully realized until decades later, thanks to a scientist named Stanley Prusiner. The killer wasn't a virus. It wasn't a bacteria, a fungus, or a parasite. It was a prion.

[00:06:31]Short for proteinaceous infectious particle, a prion is something entirely new to science. It isn't alive. It is simply a normal protein found in the brain that has accidentally folded into a corrupted microscopic monster.

[00:06:53]A prion forces nearby healthy proteins to fold incorrectly, creating a chain reaction that slowly destroys the brain.

[00:07:03]It creates a horrific domino effect.

[00:07:06]Over years, or even decades, these misfolded proteins clump together, creating microscopic holes in the brain until the tissue looks [music] exactly like a kitchen sponge. This condition is called spongiform encephalopathy.

[00:07:24]And because a prion is just a protein, not a living organism, it has no DNA to destroy.

[00:07:32]That's why heat and radiation couldn't stop it.

[00:07:36]The discovery of prions fundamentally changed our understanding of medicine.

[00:07:42]Carlton [music] Gajdusek won a Nobel Prize for proving Kuru was an infectious agent. And Stanley Prusiner [music] won one later for identifying the prion.

[00:07:54]Solving Kuru helped scientists understand [music] several deadly brain diseases including mad cow disease and Creutzfeldt-Jakob disease.

[00:08:07]But it remains a chilling reminder of [music] what happens when the smallest, simplest building blocks of our bodies go rogue.

[00:08:18]If you want to dive [music] deeper into history's strangest medical anomalies, make sure to hit that subscribe button, leave a like, and comment below on what mystery we should unravel next. Thanks for watching and stay curious.