Botulinum toxin, a protein produced by the bacterium Clostridium botulinum, could be “the most poisonous poison” there is, as writer Carl Lamanna called it in an article for Science, in 1959. First weaponized by Imperial Japan in the 1930s, and later, Nazi Germany, the United States, the Soviet Union, Syria, Iran, Iraq, and North Korea, a single gram of toxin could theoretically kill more than a million people if dispersed into the air and inhaled. But before botulinum toxin became a bioweapon and a smoother of crow's feet as the drug Botox, botulism was historically a foodborne malady, and the toxin lurked in sausage and cured meats.

Botulism, the illness caused by toxin exposure, first received scientific attention in rural Germany in the late 18th century. Officials in Stuttgart saw an increase in “sausage poisoning” in the wake of the Napoleonic wars, possibly due to poor sanitation and widespread poverty. In the 1820s, a young German physician named Justinus Kerner was the first scientist to publish an accurate and comprehensive description of the disease. He analyzed more than 200 cases of suspected sausage poisoning. He fed extracts of these “sour” sausages to animals and described the classic symptoms of botulism. Muscle weakness leading to drooped eye lids, difficulty swallowing, and respiratory failure; altered autonomic nerve function leading to vomiting, pupil dilation, and dry mouth. Brazenly, he sampled a few drops of this extract himself—he survived, though it caused a “great drying out of the palate and pharynx,” a harbinger of Botox’s modern application in treating uncontrollable salivation for those with amyotrophic lateral sclerosis, or Lou Gehrig’s disease. Grateful citizens dubbed the scientist “Wurst-Kerner,” for his pioneering contributions to public health and sausagery. In 1870, another German physician renamed the illness “botulism” after the Latin word “botulus,” or sausage.

For centuries, people dried, smoked, fermented, canned, and neglected their food, naïve to the microbial threat festering within. This changed in the late 19th and early 20th centuries as science moved from the laboratory into the kitchen. In 1895, Émile van Ermengem isolated a spore-forming bacterium from the remnants of a salted ham that killed three musicians in a Belgian outbreak. He confirmed that Kerner’s mysterious sausage—or ham—poison was made by a microbe. Under very specific growth conditions, the active form of the bacterium could be coaxed to grow and produce toxin; under other conditions, the bacterium would retreat into a dormant, or spore form that does not do so.

Early 20th century researchers found Clostridium botulinum spores nearly anywhere: in soil, rivers, lakes, oceans, on vegetable surfaces, and in fish and animal intestines. Laboratory tests demonstrated that spores are durable: they withstand even boiling. When introduced into an optimal, low-oxygen environment—like the inside of a jar or can of food—spores germinate and make the toxin. Given the ubiquity of botulinum spores in the environment, it is surprising that outbreaks were not more frequent.