From September 20 to 27, 1950, the U.S. Navy released the pathogens off the shore of San Francisco. Based on results from monitoring equipment at 43 locations around the city, the Army determined that San Francisco had received enough of a dose for nearly all of the city's 800,000 residents to inhale at least 5,000 of the particles.
On October 11, 1950, eleven residents checked into Stanford Hospital for very rare, serious urinary tract infections. Although ten residents recovered, one patient, Edward J. Nevin, died three weeks later. None of the other hospitals in the city reported similar spikes in cases, and all 11 victims had urinary-tract infections following medical procedures, suggesting that the source of their infections lay inside the hospital. Cases of pneumonia in San Francisco also increased after Serratia marcescens was released, though a causal relation has not been conclusively established. The bacterium was also combined with phenol and an anthrax simulant and sprayed across south Dorset by US and UK military scientists as part of the DICE trials that ran from 1971 to 1975.
The urinary tract outbreak was so unusual that the Stanford doctors wrote it up for a medical journal.
There was no evidence that the Army had alerted health authorities before it blanketed the region with bacteria. Doctors later wondered whether the experiment might be responsible for heart valve infections around the same time as well as serious infections seen among intravenous drug users in the 1960s and 1970s.
Senate subcommittee hearings
In the 1977 Senate subcommittee hearings, the U.S. Army disclosed the existence of the tests. Army officials noted the pneumonia outbreak in their testimony but said any link to their experiments was totally coincidental. The Army pointed out that no other hospitals reported similar outbreaks and all 11 victims had urinary-tract infections following medical procedures, suggesting that the source of their infections lay inside the hospital.
In 1981, Nevin's surviving family members filed suit against the federal government, alleging negligence and responsibility for the death of Edward J. Nevin, as well as financial and emotional harm caused to Mr. Nevin's wife from the medical costs.
The lower court ruled against them primarily because the bacteria used in the test was unproven to be responsible for Mr. Nevin's death. The Nevin family appealed the suit all the way to the U.S. Supreme Court, which declined to overturn lower court judgments.
In the Senate subcommittee hearings in 1977, the Army revealed:
- Between 1949 and 1969, open-air tests of biological agents were conducted 239 times. In 80 of those experiments, the Army said it used live bacteria that its researchers at the time thought were harmless. In the others, it used inert chemicals to simulate bacteria.
- In the 1950s, army researchers dispersed Serratia on Panama City and Key West Florida with no known illnesses resulting.
- In the 1950s, army researchers dispersed zinc cadmium sulfide (now a known cancer-causing agent) over Minnesota and other Midwestern states to see how far they would spread in the atmosphere. The particles were detected more than 1,000 miles away in New York state.
- Bacillus globigii, never shown to be harmful to people, was released in San Francisco, New York, Washington, D.C., and along the Pennsylvania Turnpike, among other places.
- In New York, military researchers in 1966 spread Bacillus subtilis variant Niger, also believed to be harmless, in the subway system by dropping lightbulbs filled with the bacteria onto tracks in stations in midtown Manhattan. The bacteria were carried for miles throughout the subway system. Army officials concluded in a January 1968 report that: "Similar covert attacks with a pathogenic disease-causing agent during peak traffic periods could be expected to expose large numbers of people to infection and subsequent illness or death."
- In a May 1965 secret release of Bacillus globigii at Washington's National Airport and its Greyhound Lines bus terminal, more than 130 passengers were exposed to the bacteria traveling to 39 cities in seven states in the two weeks following the mock attack.
- Jim Carlton,Of Microbes and Mock Attacks: Years Ago, The Military Sprayed Germs on U.S. Cities, The Wall Street Journal, (October 22, 2001).
- Leonard A. Cole, Clouds of Secrecy: The Army's Germ Warfare Tests Over Populated Areas - Special Report No. 142: "Biological Warfare Trials at San Francisco, California, 20–27 September 1950".
- "How the U.S. Government Tested Biological Warfare on America". Priceonomics. October 30, 2014. Retrieved 19 July 2016.
- Cole, Leonard A. (1988). Clouds of Secrecy: The Army's Germ-Warfare Tests Over Populated Areas. (Foreword by Alan Cranston.). Totowa, New Jersey: Rowman & Littlefield. ISBN 0-8476-7579-3.
- Regis, Ed. The Biology of Doom : America's Secret Germ Warfare Project. Diane Publishing Company. ISBN 0-7567-5686-3.
- Barnett, Antony (2002-04-21). "Millions were in germ war tests". The Guardian. Retrieved 27 October 2012.
- Bernadette Tansey, Serratia has dark history in region / Army test in 1950 may have changed microbial ecology, San Francisco Chronicle, (October 31, 2004).
- Secret Testing in the United States, The American Experience "In the event, the courts ruled against them, the main reason being that the plaintiffs could not prove that the bacteria used in the test were the same as those that killed Mr. Nevin."
- Judge's Decision Expected Soon in California Germ Warfre (sic) Case, New York Times, (April 15, 1981)