Given that with genetic engineering we can customize organisms as bio-weapons. Which species have the most worrying potential to be weaponized for mass destruction?


Biological warfare — is the use of biological toxins or infectious agents such as bacteria, viruses, and fungi with intent to kill or incapacitate humans, animals or plants as an act of war.


E.G. bio-weapon species: Anthrax fungus - was first tested as a biological warfare agent by Unit 731 of the Japanese Kwantung Army in Manchuria during the 1930s; some of this testing involved intentional infection of prisoners of war, thousands of whom died. Anthrax, designated at the time as Agent N, was also investigated by the Allies in the 1940s.

E.G. bio-weapon vector: Anopheles labranchiae (malarial mosquito) - According to Prof Frank Snowden, a history professor at Yale University whose book The Conquest of Malaria in Italy draws on American archives and the diaries of Italian soldiers, the scheme was orchestrated in the autumn of 1943 by Erich Martini, a medical entomologist, Nazi Party member and friend of the SS commander Heinrich Himmler.

  • $\begingroup$ When was anthrax used to assassinate US politicians? $\endgroup$
    – Alan Boyd
    Dec 12, 2013 at 17:43
  • 1
    $\begingroup$ You remember these mysterious letters in the US following 9/11 containing a white powder? This were actually weapon grade anthrax spores. $\endgroup$
    – Chris
    Dec 12, 2013 at 19:08
  • $\begingroup$ @AlanBoyd, here's the wiki all about it: en.wikipedia.org/wiki/2001_anthrax_attacks, i've updated the question to include some details on this $\endgroup$ Dec 12, 2013 at 19:15
  • $\begingroup$ Which confirms that no politicians were assassinated. $\endgroup$
    – Alan Boyd
    Dec 13, 2013 at 7:38
  • 2
    $\begingroup$ I would say by far the most worrying potential is that of H.sapiens sapiens. $\endgroup$
    – terdon
    Dec 18, 2013 at 14:39

4 Answers 4


There is both a set "list" of agents, but more importantly, a set of properties that an organism needs to be in order to be truly worrisome.

First, the list:

The CDC classifies agents into one of three categories, Class A, B, or C.

Class A: These are organisms that are hard to control, highly transmissible, and lethal:

Anthrax (Bacillus anthracis)
Botulism (Clostridium botulinum toxin)
Plague (Yersinia pestis)
Smallpox (variola major)
Tularemia (Francisella tularensis)
Viral hemorrhagic fevers (filoviruses [e.g., Ebola, Marburg] and arenaviruses [e.g., Lassa, Machupo])

Class B: These are organisms that are fairly easy to disseminate, make people sick but don't necessarily have high mortality rates, and may be difficult to detect.

Brucellosis (Brucella species)
Epsilon toxin of Clostridium perfringens
Food safety threats (e.g., Salmonella species, Escherichia coli O157:H7, Shigella)
Glanders (Burkholderia mallei)
Melioidosis (Burkholderia pseudomallei)
Psittacosis (Chlamydia psittaci)
Q fever (Coxiella burnetii)
Ricin toxin from Ricinus communis (castor beans)
Staphylococcal enterotoxin B
Typhus fever (Rickettsia prowazekii)
Viral encephalitis (alphaviruses [e.g., Venezuelan equine encephalitis, eastern equine encephalitis, western equine encephalitis])
Water safety threats (e.g., Vibrio cholerae, Cryptosporidium parvum)

And finally, Class C, which are emerging threats that may be dangerous if engineered largely due to their novelty and their potential lethality/transmissability. The CDC uses examples like Nipah virus and hantavirus.

So that's the list of what the CDC thinks is a big deal. You'll note influenza isn't even on there. I'd argue that any given novel influenza strain belongs in Class C, and likely not Class A because, while potentially both transmissible and virulent, a known vaccine exists and simply needs to be formulated.

In terms of properties for an organism, I'd suggest the following, in no particular order (it likely depends on what said organism is meant to do):

  • Highly virulent: The disease needs to be able to cause human disease, with high rates of both morbidity and mortality.
  • Highly transmissible: Unless the goal is to cause a "one off" incident, the disease needs to be able to establish a productive chain of human-to-human infections. Humans can't be a dead-end host. Ideally, this needs to be direct human to human transmission, rather than a vector born disease like West Nile.
  • Stable and amenable to engineering. It needs to be something that's easy to culture and grow in large numbers. This one often gets overlooked somewhat, but despite the fact that its now somewhat commonplace, bioengineering isn't exactly easy.
  • Not amenable to treatment. The organism needs to not be easily treatable - broad spectrum antibiotics, existing vaccine stock, etc. mean that the normal public health infrastructure can address, or at least mitigate, an attack. For an attack to be truly effective, it needs to swamp existing infrastructure, and one way to do that is to necessitate intensive, unusual care in hospitals and out of the ordinary action on the part of public health officials.

No doubt influenza. The horizontal shift makes it very virulent and only a few mutations allow it to transfer from birds to mammals (as little as two). See here. There was a big push not to publish these as it would be so easy to make recombinantly. However, thanks to quick work, we have determined that our seasonal flu vaccine protects against this variant.


I would put all zoonotic viruses into this. They passed a species barrier, are new to our immune system and there are no vaccines against them. The flu is one example, corona viruses are another (SARS or even newer MERS). With SARS we had a lot of luck that this didn't end in a bigger epidemic. A good book about these viruses is the book "Outbreak" (hence the title) by David Quammen.


A more abstract idea for a Bioweapon species could be one that targets key organisms required for completing the nitrogen or carbon cycle. This would likely cause the entire biosphere to collapse though.


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