The world’s first anthrax outbreak begins in Sverdlovsk, Russia (now Ekaterinburg), on April 2, 1979. By the time it ends six weeks later, according to official records, 66 people had died and some 30 more had 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.