Bay Curious When Biological Weapons Were Secretly Tested in San Francisco
Nov 6, 2025
Katherine Monahan, a reporter at KQED, dives into the shocking historical account of Operation Sea Spray, a covert U.S. military biological weapons test in San Francisco in 1950. She reveals how harmless bacteria were sprayed over the city, leading to illnesses and even one death. Monahan discusses the military's motivations, the public outcry that followed, and the ethical implications of such tests. She also shares the poignant story of the Nevin family, who uncovered their grandfather's link to the operation, culminating in a significant lawsuit against the government.
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Covert Coastal Bioweapon Testing
- In 1950 the military secretly sprayed bacteria over San Francisco to test dispersal from a ship offshore.
- The test used supposedly harmless microbes to model how a city might be exposed to a biological attack.
Visible Microbes Measured Citywide Spread
- The army tracked dispersal using visible and easily culturable bacteria to measure reach across the Bay Area.
- Monitors found the spray reached as far as 23 miles and exposed thousands at normal breathing rates.
Hospital Outbreak After The Spray
- Stanford Hospital saw eleven patients develop Serratia marcescens infections after the spray, and one patient died.
- Dr. Matthew Meselson later learned a lab assistant's tip linked the military test to that death.