Why YSK: This incident revealed the existence of Aralsk-7, a secret Soviet bioweapons facility located on what became known as Plague Island. There, Soviet scientists developed and tested weaponized pathogens like smallpox, plague, and anthrax—a direct violation of international treaties.

The 1971 outbreak, caused by exposure to an aerosolized smallpox release, was quietly contained and covered up. It only came to light decades later through declassified intelligence and testimony from Soviet defector Ken Alibek.

It’s important to know because it highlights how close the world came to an accidental pandemic—and how dangerous hidden bioweapons programs can be, even today.