Weapons of mass destruction include: nuclear, radiological, biological and chemical weapons – the last two overlap greatly. Biological weapons are defined as bacteria, viruses or protozoans specifically bred for this purpose, or synthetically created poisonous organic matter.
 
Forms of biological weapons
Viral pathogens like smallpox and yellow fever virus, amongst bacteria the Brucella genus, Francisella tularensis, Bacillus anthracis or Yersinia pestis could be used as biological weapons. The Brucella genus is especially suitable for this purpose: it can cause relapsing fevers, arthritis, miscarriage, or even infertility – it takes weeks to treat. As it was said on a microbiology lecture: whoever catches it will lose the will to fight, and to do anything for a long time.
The chosen microbe can be delivered to its location in many ways: infecting the food, or the water supply, delivered in the air as aerosol, on a rocket, or using insects as vectors. Warfare using infected or uninfected insects is called entomological warfare.
 
History – even Hitler forbade it
Biological warfare goes far back – even in the ancient times when the army marched onwards, they threw dead bodies in the wells, to cut the following army off from a source of clean water. Wars were and still are regularly followed by epidemics, often taking more lives than the fight itself did. During sieges in the middle ages, it was uncommon but still happened that dead bodies or even human feces were catapulted behind enemy lines.  
During the first world war next to chemical weaponry – like gases – biological weapons were also utilized, but they were mostly used against animals. The pathogens were developed in the German embassy, and spies used them to infect the horses and mules of the enemy forces. They still hurt the enemy without infecting people.
In the second world war, England and France were at the forefront of research, they were under the impression that the Reich had the advantage because they had previous experience in organized biological warfare. Interestingly, Hitler forbade the research and usage of these weapons.
The English created the aerosol bomb, that could scatter the pathogen that causes anthrax – Operation Vegetarian, if it were carried out, that would’ve meant scattering Bacillus anthracis on many places where they fed cows. This would’ve caused serious famine; anthrax can even spread to humans; furthermore, anthrax is so potent it would’ve made the area of the explosion unapproachable for many years.

This is illustrated brilliantly by the testing of the bomb – it was detonated on an uninhabited Scottish island: Gruinard. The sheep delivered to the island soon caught and died from anthrax, one could say the experiment succeeded – maybe even a little too well. The consequences answer the question posed in the title: there have been many attempts at disinfecting the island, but forty years after the detonation, there’s still infectious spores found in the soil.
The 1925 Geneva Conventions only banned the use of biological weapons, not the development or possession – the latter of which was banned in 1975. Japan didn’t sign any of these treaties, this can still be seen in its tactics: between the two world wars, they used bombs in Manchuria that were filled with infected fleas, on the other occasion they gave infected food to the starving population of a war-torn China.
 
Recently – envelope terrorism
It started right after the turn of the century. Envelopes infected with B. anthrax were used for terrorism. Many media providers in the USA, like news outlets and television channels got infected letters. It also arose that many private letters were infected by the spore carrying envelopes. These envelopes are considered biological weapons, and as terror attacks, a connection between the sender and the terrorists who flew a plane into the Twin Towers was found.
In Hungary, many suspicious packages and envelopes reached their targets, but no tragedies occurred. The stance of the authorities was to not be frightened but to be prepared for possibly infectious mail. Thankfully the panic and unneeded alarms and sending baby powder and face powder in envelopes have subsided since then.
 

This article is not sponsored by the Institute of Medical Microbiology.