Some Current Bio-agent Considerations

Biological Agents

The NFPA 1994 Standard on Protective Ensembles for First Responders to CBRN Terrorism Incidents defines “biological terrorism agents” as: “Liquid or particulate agents that can consist of a biologically derived toxin or pathogen used to inflict lethal or incapacitating casualties, generally on a civilian population as a result of a terrorist attack.”

The time lapse between release of an agent and its discovery is frequently longer for biological agents than chemical agents. Chemical agents typically (although there are exceptions) have an immediate impact, with symptoms manifesting upon exposure. By contrast, the release of a biological agent may not be detected for days, weeks, or months given the latency between exposure and onset of symptoms in the host/victim unless the release is detected through an early warning system such as the BioWatch System that the Department of Homeland Security (DHS) manages and EPA supports.
Homeland Security Presidential Directive 18: Medical Countermeasures against Weapons of Mass Destruction identifies four categories of potential biological agents. They are:
Traditional agents are naturally occurring microorganisms or toxin products that can be weaponized and disseminated to cause mass casualties. Aerosolized agents (such as aerosolized anthrax) pose particularly challenging hazards. Such materials are easily spread by air currents and can be re-aerosolized by slight movements or disturbances in air currents.¹

Enhanced agents are organisms that are modified to circumvent current countermeasures (e.g., microorganisms that are intentionally manipulated to be resistant to multiple antibiotics).

Emerging agents are naturally occurring agents but are newly recognized or anticipated to pose a public health threat (e.g., a highly lethal and readily transmissible influenza strain that may cause a pandemic).

Advanced agents are novel microorganisms created in the laboratory.
CDC classifies biological agents into three priority categories: A, B, and C. These categories are described in Table 2 below. CDC’s Bioterrorism Agents/Diseases website provides more information on these categories as well as many of the specific agents. (Note: Table 2 lists bioagents as examples only and does not present a definitive list. Also, these items reflect CDC classifications only and do not necessarily represent which agents pose the greatest toxicity or risk.)
Table 2
CDC’s Agent Classifications and Example Biological Agents

CDC Agent Classifications	Example Agents^a,b
Category A agents: High-priority agents that are rarely seen in the United States and pose a risk to national security because they: Can be easily disseminated or transmitted from person to person Result in high mortality rates and have the potential for a major public health impact Might cause public panic and social disruption Require special action for public health preparedness	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])
Category B agents: Second-highest-priority agents, which: Are moderately easy to disseminate Result in moderate morbidity (illness) rates and low mortality rates Require specific enhancements of CDC’s diagnostic capacity and enhanced disease surveillance	Brucellosis (Brucella species) Glanders (Burkholderia mallei) Psittacosis (Chlamydia psittaci) Q fever (Coxiella burnetti) Ricin toxin from castor beans Staphylococcal enterotoxin B Typhus (Rickettsia prowazekii)
Category C agents: Third-highest-priority agents—emerging pathogens that could be engineered for mass dissemination in the future because of: Availability Ease of production and dissemination Potential for high morbidity and mortality rates and major health impact	Nipah virus Hantavirus

^a Biotoxins are identified as chemical agents within CDC’s classification system and are therefore listed in Table 1. (Note: CDC lists ricin as both a chemical and biological agent, so ricin is listed in Tables 1 and 2.) Consensus has not been achieved regarding how to classify biotoxins. This chapter follows CDC’s classification system.
^b Links have been provided for agents if they are available.
Given the wide spectrum of biological agents and possible symptoms and health effects, a comprehensive discussion of all biological agents is beyond the scope of this chapter. The following resources provide detailed information on specific biological agents:

• 
  CDC’s “Emergency Preparedness and Response” website.
  
• 
  NRT’s Quick Reference Guides for biological agents, many of which are cross-listed with the CDC agents. The Quick Reference Guides are available for downloading at NRT’s website.
  
• 
  U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID)’s Defense Against Toxin Weapons.
  
• 
  USAMRIID’s Medical Management of Biological Casualties Handbook.
  

• 
  “Bioterrorism,” Infectious Diseases Society of America.
  

4.2.1 BioWatch

BioWatch is a nationwide bio-surveillance system, designed to detect the individual release of select aerosolized biological agents. EPA may be responsible for leading operational planning with state and local first responders and health departments, and may execute environmental sampling necessary to verify a biological release. EPA also serves as the primary contact for state and local environmental monitoring agencies during a biological agent incident (see Text Box 4). Each EPA region has at least one BioWatch Coordinator.