the secret bacteriological experiment carried out on San Francisco in 1950

In 1981, a US court closed the case initiated by the grandchildren of Edward J. Nevin, who had sued the federal government for being responsible for the death of their grandfather due to negligence that also had as a side effect the ruin of the grandmother for payments doctors. It was not a normal case, since, according to the relatives, the death was due to a bacteriological infection caused directly by a US Navy experiment on the civilian population.

The alleged events took place thirty years earlier, during the month of September 1950. Bacteriological weapons were a novelty if we refer to them stricto sensu and we ignore the historical news about epidemics deliberately caused with plague or smallpox, which often have more legend than reality. It was in the First World War when scientific experiments began with microbes for their military application, although in that war interest was focused on mustard gas, chlorine or phosgene until their definitive prohibition -theoretically- by the Geneva Protocol of 1925.

The initial singing voice in these investigations was taken by Japan through the sinister Unit 731, initially called the Kamo Unit and created in 1932 for the control of epidemics, although with the advent of World War II its interest changed to just the opposite: the infection of enemy troops and the development of biological weapons, experimenting with thousands of Chinese prisoners. It seems that it was then that anthrax was tested for the first time and also in a covert way, contaminating food.

British soldiers wearing gas masks in World War I/Photo: Public Domain on Wikimedia Commons

The Japanese were not the only ones to work in this field, as the Germans and the British also did. Likewise, the US incorporated a research plan, relying on some of the Japanese scientists from Unit 731 and other Germans. The first steps were taken in 1942 in Fort Detrick, Maryland, where USAMRIID (United States Army Medical Research Institute of Infectious Diseases) is located today, developing it in parallel with the other major arms sector of the post-war period, the atomic.

But it was in the following decade that things really moved forward, in part spurred by the outbreak of the Korean War. The striking thing about the matter was that a program of experimentation with the population was designed to verify the effects in the most accurate way possible, since the Bacteriological Warfare Committee created in 1948 warned of the susceptibility of the United States to an attack of this nature. For this, it was necessary to disseminate the pathogens in cities, so that they dispersed naturally as it would be done in a real situation, thus being able to record, quantify and analyze the results in various areas and different atmospheric conditions. San Francisco was the first city chosen for what was baptized as Operation Sea-Spray.

It consisted of spraying forty-three locations in the Bay Area, calculating that they could affect a segment of inhabitants between five and eight hundred thousand. Of course, despite the fact that the final object of the investigation only consisted of assessing the susceptibility of a large city to a biological attack, either from a defensive or offensive point of view, it was estimated that the effects during the experiment would be almost imperceptible, given that the number of bacteriological agents used was limited and what was really wanted at the moment was to see how they dispersed in order to design an optimized countermeasure plan.

San Francisco Bay/Image: Google Maps

The problem was in these agents: one was a bacterium called Bacillus globigiia variety of Bacillus atrophaeus used in medicine for biocontainment. but the other was Serratia marcescensa bacillus that develops preferentially in conditions of high humidity -it is usually found in sewers and hospitals- which in 1950 was thought to be harmless but it was a mistake, since it causes multiple symptoms that are sometimes mild (conjunctivitis, kidney infections and urinary) and other serious (respiratory problems and even meningitis).

Both were scattered from a navy minesweeper accompanied by cadmium-zinc sulfide particles to facilitate monitoring. Over the course of a week between September 20 and 27 of that year, the ship’s hoses released emissions into the air that lasted half an hour, making a total of four of them. Bacillus globigii and two of Serratia marcescens that formed a contagious invisible cloud of more than three kilometers in length. The experiment was considered a threatening success: it was feasible to cause an infection in an urban center quite easily and imperceptibly.

Cultivation of Serratia marcerescens/Photo: Benutzer:Brudersohn on Wikimedia Commons

Then came the unforeseen damage. Shortly thereafter, on October 11, eleven people were rushed to Stanford Hospital with pneumonia and urinary tract infections so uncommon in diagnosis and coincidence that one of the doctors would publish a study on the matter in a prestigious medical journal. Ten of those patients recovered and were discharged soon after, but the eleventh – actually the first, a seventy-five-year-old man who underwent prostate surgery – was unlucky and died in just three weeks from endocarditis, which is another damage that can cause Serratia marcescens after traveling to the heart from the urinary tract through the blood. The unfortunate one was Edward J. Nevin.

That strange spike in income and the presence of Serratia marcerensuntil then unpublished in the hospital, sowed some confusion but since it was not repeated the thing fell into oblivion until in 1977, in an appearance before the Subcommittee on Health and Scientific Research of the Senate and that type of tests were already canceled by Nixon in 1969, the US Navy publicly admitted carrying out the Operation Sea-Spray and had not warned the health authorities of the experiment. Not only that, but between 1949 and 1969 he had also carried out another 239 similar tests in the open air using bacteria or chemical agents that imitated them.

Of course, emphasizing that they were all innocuous and that the cases referred to had nothing to do with it, being just an anomalous coincidence, as demonstrated by the fact that in that decade spraying of this type had been repeated in Panama City and Key West (Florida) without problems. , as in later years in other places such as New York, Washington or Pennsylvania. In some of them even using again Bacillus globigii, as was done at Washington National Airport in 1965; in others, as in New York the following year, with a variety called Bacillus subtilis Nigerwhich was launched on the Manhattan subway and did not cause any damage.

They also pointed out that no other hospital in San Francisco had registered anything similar, so the eleven patients fell ill during normal medical procedures; that is, the source of infection would be in the hospital complex itself. But the medical establishment wondered if other cases of the time that had a considerable upturn – coronary infections and pneumonia, as well as a rise in intravenous infections among drug addicts in the 1960s and 1970s – were also related. In fact, cadmium-zinc sulfide is now considered a carcinogen.

All of this raised doubts in Nevin’s descendants, one of whose grandsons, Edward J. Nevin III, was a lawyer and filed a lawsuit in the San Francisco District Court in 1981. After a series of delays and even the attempted assault of a general, saw the judge decide to dismiss it, finding no conclusive correlation, arguing that no victims had been recorded at the other sites and that not even cadmium-zinc sulfide had significantly increased cancer in Minnesota, one of the states where was specifically sprayed. Nevin appealed to the Supreme Court, but it upheld the sentence, agreeing with the State attorney, who argued that there were two different strains that coincided in time and place.


In 1950, the US Released a Bioweapon in San Francisco (Helen Thompson in smithsonian)/Bacteria and bayonets. The impact of disease in american military history (David Petriello)/Operation Sea-Spray (Lisa Lumar)/US Army Activity in the US Biological Warfare Program, 1942-1977/Wikipedia