Declassified Code Names for Biological Weapons Agents

Anthrax was agent "N." Bubonic plague was agent "LE." Here's a list of all the declassified secret code names used in the U.S. germ warfare program that I was able to find.

“Researchers working with Class III cabinets at the U.S. Biological Warfare Laboratories, Camp Detrick, Maryland (1940s).” (link). Photo from Cutting Edge: A History of Fort Detrick, Maryland, 1943-1993, pg. 22, US government publication

During the years of the U.S. military program to research new methods to conduct biological warfare (BW), essentially from 1942 to 1969, the various viruses and bacteria experimented upon or tested were often referred to by top secret code names. Only those “read in” to the BW program — mainly scientists and military officers at the Chemical Warfare Service (later known as the Army Chemical Corps), the Air Force, and the CIA — knew what the obscure code letters referenced.

Today, most of these code names have been declassified, but it’s difficult to find a list of all these code names and their referents in one single place. I thought it would be apropos to collect these now declassified descriptors.

The material below was once posted as an appendix to an earlier article I wrote. It seemed a shame to bury such important reference material that way, so I am publishing it, with a few updates since original publication, as a stand-alone post. Feel free to bookmark it, print it, share it, or even repost it yourselves (with a link back to this article, please).

One caveat: this list cannot, unfortunately, be considered definitive. This is due to the still classified nature of much of what was the U.S. BW research and weapons programs. As I come across more code names or cryptonyms, I will add them to this article, so it may be useful to check back in from time to time to see if I’ve added anything new. Readers who have further information or relevant links, please leave them in the comments section of the online version of this article.

Code Names for Biological Agents

The various biological agent names are presented below in alphabetic order, as found in Rexmond Cochrane’s, November 1947 monograph, “Biological Warfare Research in the United States,” Volume 2, pp. 518-519.

Items marked with an asterisk reference additional BW agents as discussed in Weapons System Evaluation Group [WSEG] Report No. 8, “An Evaluation of Offensive Warfare Weapons Systems Employing Manned Aircraft, Enclosure ‘E’, Characteristics of Anticrop Agents, Munitions, and Weapons Systems”, pg. E-32. Also, I have included a few code names for chemical agents that are often seen in scattered documents that discuss biological weapons and agents.

Agents injurious to rice — Code “II”
Anthrax — Code “N”
Bacillus atrophaeus aka B. globigii — Code “BG” [“Its original and still most prominent use is as a surrogate organism for pathogenic B. anthracis [anthrax], beginning in the U.S. bio-weapons program….” (link)]
Botulism — Code “X”
Brown Spot of Rice — Code “E”
Brucellosis — Code “US”
Cholera — Code “HO”
Coccidioides, aka San Joaquin Valley fever — Code “OC”
Dysentery — Code “Y”
Experimental Agent, generic — Code “EA” [The acronym may also have stood for “Edgwood Arsenal,” and usually described chemical compounds. Examples include EA 1729 and EA 3528 for LSD; EA 1701 for VX nerve gas; and EA 2277 for the incapacitating agent BZ (link).]
Feathers as Agent Carrier* — Code “M1”
Foot and Mouth Disease — Code “OO”
Fowl Plague & Newcastle Disease — Code “CE”
Glanders — Code “LA”
Japanese Type B Encephalitis — Code “AN”
Late Blight of Potato — Code “LO”
Mass Culture of Spores — Code “AU”
Melioidosis, aka Whitmore’s Disease — Code “Hi”
Mussel Poisoning — Code “SS”
Neurotropic encephalitises — Code “NT”
Plague — Code “LE”
Plant Growth Regulating Substance — Code “LN” [There were a number of subtypes of these; for example, 2,4-Dichlorophenoxyacetic acid (2,4-D) was codenamed “LN8”]
Psittacosis, aka “Parrot Fever” — Code “Si”
Rice Blast — Code “IR”
Rickettsiae — Code “RI”
Rinderpest — Code “R” or “GIR 1”
Sclerotium Rot, aka Southern Blight — Code “C” or “Co”
Stem Rust*, aka cereal rust, specifically Puccinia graminis tritici (causes disease in cereal crops, wheat, barley, triticale) — Code “TX”
Tularemia — Code “UL”
Typhus — Code “YE”

This article was adapted and updated from an earlier article originally published as “Secret Report: US Military Approved Offensive Use of Biological Warfare on Enemy Agriculture in World War 2,” published at Medium.com on May 14, 2018. An updated version was published at Hidden Histories on April 11, 2025.