Fog of Infection: Operation Sea-Spray

In 1950, a U.S. Navy ship off the coast of San Francisco released a cloud of bacteria into the city. Residents had no idea. Some got sick. One died.

This episode of Unsettled: The Hidden Record investigates Operation Sea-Spray, a secret U.S. military experiment designed to simulate a biological attack on a major American city. Using what were believed to be “harmless” bacteria, the military sprayed Serratia marcescens over the Bay Area to study how a pathogen might disperse in an urban environment.

The experiment was never disclosed to the public. When rare infections began to appear, the military denied involvement. It took years—and declassified documents—to uncover what really happened.

Was this just a miscalculated test? Or the quiet normalization of biological warfare on domestic soil?