Contaminated milk from one plant in Illinois sickened thousands with ‘Salmonella’ in 1985 − as outbreaks rise in the US, lessons from this one remain true

A valve that mixed raw milk with pasteurized milk at Hillfarm Dairy may have been the source of contamination. This was the milk processing area of the plant. AP Photo/Mark Elias

In 1985, contaminated milk in Illinois led to a Salmonella outbreak that infected hundreds of thousands of people across the United States and caused at least 12 deaths. At the time, it was the largest single outbreak of foodborne illness in the U.S. and remains the worst outbreak of Salmonella food poisoning in American history.

Many questions circulated during the outbreak. How could this contamination occur in a modern dairy farm? Was it caused by a flaw in engineering or processing, or was this the result of deliberate sabotage? What roles, if any, did politics and failed leadership play?