The world’s first anthrax epidemic begins in Ekaterinburg, Russia (now Sverdlosk), on this day in 1979. By the time it ended six weeks later, 62 people were dead. Another 32 survived serious illness. Ekaterinburg, as the town was known in Soviet times, also suffered livestock losses from the epidemic.

As people in Ekaterinburg first began reporting their illnesses, the Soviet government announced that the cause was tainted meat that the victims had eaten. Since the town was known in intelligence circles for its biological-weapons plant, much of the rest of the world was immediately skeptical of the Soviet explanation.

It was not until 13 years later, in 1992, that the epidemic was finally explained: workers at the Ekaterinburg weapons plant failed to replace a crucial filter, causing a release of anthrax spores into the outside air. The wind carried the spores to a farming area and infected people and livestock in the area. Had the town been downwind from the plant at the time of the release, the death toll might have been considerably higher.

Anthrax is a bacterium that can enter the body through multiple routes. It is most deadly when it is inhaled. It prompts the production of toxic molecules that destroy essential proteins in the body’s cells, usually in the lymph nodes.

In 2001, anthrax spores were used as a weapon of terror in the United States. Spores were mailed to media organizations and members of the U.S. Senate. Five people died and another 13 were infected, but survived. The investigation into who was responsible is ongoing.