In the history of Earth in the Aura Universe, the discovery of prions had been exceptionally tortuous.
In fact, the first human-infectious disease studied whose pathogen was a prion, Human prion disease, had been discovered as early as 1955. At the time, an American explorer and physician named Gajdusek had discovered it while investigating a primitive tribe with cannibalistic customs in the eastern highlands of Papua New Guinea.
This American doctor had even concluded that the disease known as "Kuru disease" was caused by that cannibal tribe consuming the brains of their dead relatives.
He used chimpanzees as experimental animals, diluted homogenized brain tissue taken from Kuru disease patients after their deaths, and injected it into the chimpanzees.
Afterward, he successively used physical means to separate out larger bacteria and parasites, and used ultraviolet light to destroy nucleic acids, in order to identify the pathogen of Kuru disease.
He had even tried treating those homogenates with proteolytic enzymes.
Of course, without question, the proteolytic enzymes had caused those homogenates to completely lose their pathogenicity.
But his first reaction had been... well, the proteolytic enzymes must have destroyed the shell of the "Kuru disease virus."
This should have been a new kind of virus.
At the time, that idea had been perfectly natural—or rather, nearly every scholar would have thought the same way.
When Gajdusek discovered Kuru disease and gave it an inaccurate... no, even erroneous conclusion, Prusiner, the future discoverer of prions, had only just entered middle school.
And that achievement had earned Gajdusek the Nobel Prize in Physiology or Medicine in 1976.
Meanwhile, Prusiner had still been pondering in his childhood whether to use hamsters with an incubation period of only one hundred days instead of mice with an incubation period of two hundred days.
Incidentally, the first prion