Biological warfare is the use of microbiological agents as weapons. Such use is contrary to international law and has rarely taken place during formal warfare in modern history, despite the extensive preparations and stockpiling of biological agents carried out during the 20th century.
Biological weapons are thought by some to be ideal weapons for terrorists. These agents may be delivered in secret and have delayed effects, allowing the perpetrator to remain undetected.
The US Centers for Disease Control and Prevention (CDC) has created a priority list of biological agents and toxins (see table CDC High-Priority Biological Agents and Toxins). The highest priority are Category A.
The deliberate use of biological weapons to cause mass casualties would probably entail the use of aerosols. Inhalational anthrax and pneumonic plague are the two diseases most likely to occur under these circumstances.
CDC High-Priority Biological Agents and Toxins
A: Highest priority
Bacillus anthracis, causing anthrax
Botulinum toxin from Clostridium botulinum, causing botulism
Yersinia pestis, causing plague
Francisella tularensis, causing tularemia
Variola virus, causing variola major (classic smallpox)
B: 2nd highest priority
Brucella species, causing brucellosis
Epsilon toxin of Clostridium perfringens, causing food poisoning
Burkholderia mallei, causing glanders
Burkholderia pseudomallei, causing melioidosis
Chlamydia psittaci, causing psittacosis
Coxiella burnetii, causing Q fever
Ricin toxin from Ricinus communis, causing different symptoms depending on type of exposure
Staphylococcal enterotoxin B, causing staphylococcal food poisoning and other symptoms depending on type of exposure
Rickettsia prowazekii, causing typhus fever
Alphaviruses causing viral encephalitides (for example, Venezuelan, eastern, and western equine encephalitides)
C: 3rd highest priority
Other agents associated with emerging infectious diseases
CDC = U.S. Centers for Disease Control and Prevention; SARS = severe acute respiratory syndrome.
*An alphabetical listing of bioterrorism agents and diseases can be found at Centers for Disease Control and Prevention: Emergency Preparedness and Response.
Distinguishing the use of a biological weapon from a natural outbreak of disease may be difficult for doctors. Clues to a deliberate rather than a natural origin of a disease outbreak include the following:
- Cases of diseases not usually seen in that geographic area
- Unusual distribution of cases among segments of the population
- Significantly different illness rates between those inside and those outside buildings
- Separate outbreaks in geographically diverse areas
- Multiple simultaneous or serial outbreaks of different diseases in the same population
- Unusual routes of exposure (such as inhalation)
- A disease that normally affects animals occurring in humans
- A disease that normally affects animals arising in an area where that animal species is not usually present
- Unusual severity of disease
- Unusual strains of infectious agents
- Failure to respond to standard therapy
The symptoms, diagnosis, and treatment of people with the following diseases caused by high-risk biological weapons are discussed elsewhere in The Manuals:
Doctors may need to isolate people exposed to a biological weapon and place under quarantine people known to have been in contact with an exposed person.
Because of the relatively long incubation periods of diseases caused by biological weapons, people will likely be treated in a hospital. People are given vaccines, antibiotics, or antiviral drugs depending on the specific infectious organism involved. Sometimes people who have been in contact with the affected people are given preventive treatment. For many biological weapons, there is no specific treatment or vaccine.
The views expressed in this article are those of the author and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.
- Centers for Disease Control and Prevention: Emergency Preparedness and Response