Historically, naturally occurring endemic diseases have significantly affected military personnel and impacted operations.18,19  Specifically, diarrhea and respiratory infections have resulted in the most morbidity and lost days of work during deployments.20,21  The totality of the potential biothreat environment is summarized in Figure 2. Medical intelligence can provide situational awareness of biothreats for the operational environment. Given the unique problem set and due to space constraints, this documents’ focus will primarily be on biowarfare agents directed at humans as a base, but including endemic and emerging diseases. Biowarfare agent characteristics will be summarized to aid understanding in later sections. For more detailed information, see the references for this section. 

Figure 2. Potential biothreat challenges

Specific biothreats have been identified by their innate characteristics to pose an increased risk to national security, and have been termed Category A, B, and C agents/diseases by the Centers for Disease Control and Prevention (CDC).22  For example, Category A agents/diseases pose a risk to national security given that they: can be easily disseminated or transmitted from person to person, result in high mortality rates, have the potential for a major public health impact, might cause public panic/social disruption, and require special action for public health preparedness.22 Category A agents include:

  • Anthrax (Bacillus anthracis).
  • Botulism (Clostridium botulinum toxin).
  • Plague (Yersinia pestis).
  • Smallpox (Variola major).
  • Tularemia (Francisella tularensis).
  • Viral hemorrhagic fevers:
    • Filoviruses: Ebola, Marburg, etc.
    • Arenaviruses: Lassa, Machupo, etc.

Note that these biothreats can generally be encountered in nature as endemic diseases or toxins produced/encountered via exposure to natural sources with the exception of smallpox, which has been eradicated from the human population. 

Biothreats can be produced, weaponized, and disseminated via simple or complex means, depending on the agent and goals/capabilities of the adversary.23-26  Specific biothreats can be chosen to cause incapacitation, death, fear and to degrade the mission with deniability. Biothreats can be noncontagious, with effects limited to individuals directly exposed or contagious, to enable secondary spread to other units, allied and partner forces, host nation civilians, or the U.S. civilian population.3  Goals of use could range from targeted assassination to widespread disruption of key areas (logistics nodes, command and control centers, and hubs needed for force flow) during a military operation thereby reducing combat power in units at critical phases of conflict.3,24,25 Medical and public health personnel should have an understanding of dissemination mechanisms of biowarfare agents to enable recognition of a deliberate biological incident, guide surveillance, triage, and medical evaluations. Potential dissemination mechanisms described in published open sources could include:23,24,27

  • Deliberate infection of an individual or group of individuals with a contagious disease who then cause secondary spread in a target population.24
  • Direct injection: Typically, would be used for assassinations.24,27The most well-known example is the assassination of Georgi Markov with ricin.27
  • Water contamination.24,27
  • Food or beverage contamination.24,27
  • Vector introduction27:The most well-known example was Imperial Japan’s use of air dropped plague-infected fleas in China during World War II.27
  • Aerosol dissemination:24,27
  • Point source delivery:24,27 Agent delivered from a single source.
    • Traditionally, via an explosive munition, which may reduce the viability of some pathogens.24
    • Placing a spray device into the air intake duct of a building’s air handling system, or as simple as a smashed flask, or via a letter.24,27
  • Multiple point source delivery:24 Multiple single point sources.Traditional example could be via bombardment or multiple dispersal devices coordinated by timing mechanisms.24
  • Line source delivery:24,27 Moving delivery device releases a flow of agent over an extended period.Examples could include a crop duster, an agricultural drone, or a vehicle with a sprayer.24

The threat of biowarfare agents is further augmented by the rapid evolution of scientific fields and technologies such as synthetic biology. Synthetic biology is a rapidly growing field with the potential of revolutionizing the medical field. According to the CDC, synthetic biology may have significant consequences because engineered modifications could:

  1. generate or acquire an eradicated pathogen.
  2. enhance the harmful properties of a current pathogen.
  3. disrupt immunity or the effectiveness of vaccines against pathogens.
  4. confer properties to evade methods of detection/diagnostics.
  5. enhance the susceptibility of a host population to a pathogen.
  6. increase stability, transmissibility.
  7. alter host range or tissue tropism.
  8. obfuscate attribution28.