Agents

Category A Agents

Category A agents are the highest-priority agents because they:

• Can be easily disseminated or spread person-to-person
• Can be extremely lethal
• Have the potential for serious public health impact
• Can potentially cause public panic and lead to social disruption 

Category A organisms include:

• Bacillus anthracis (anthrax)
• Clostridium botulinum (botulism)
• Yersinia pestis (plague)
• Variola major (smallpox) and other pox viruses
• Francisella tularensis (tularemia)
• Viral hemorrhagic fevers

Category B Organisms

Category B organisms are the second-highest-priority agents because they:

• Are moderately easy to disseminate
• Usually result in moderate morbidity
• Are generally less lethal 

Category B organisms include:

• Burkholderia pseudomallei
• Coxiella burnetti (Q fever)
• Brucella species (brucellosis)
• Burkholderia mallei (glanders)
• Ricin toxin (from Ricinus communis)
• Epsilon toxin of Clostridium perfringens
• Staphylococcus enterotoxin B
• Typhus fever (Rickettsia prowazekii)
• Other food and waterborne pathogens 

Category C Organisms

Category C organisms are defined as:

• Emerging infectious disease threats that potentially could be engineered for future dissemination

Category C organisms include:

• Nipah virus
• Additional hantaviruses

See also the CDC's list of Biological Agents/Diseases and NIAID's Category A, B & C Priority Pathogens.