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First Hours: Bioterrorism Agents


Bioterrorism agents are separated into three categories—A, B, or C (see the CDC Bioterrorism Overview)—depending on how easily they can be spread and the severity of illness or death they cause.

  • Category A agents are considered the highest risk and the highest priority.
  • Category B agents are the second highest priority.
  • Category C agents are the third highest priority and include emerging pathogens that could be engineered for mass spread in the future.

Category A agents include organisms and toxins that pose the highest risk to the public and national security for the following reasons:

  1. They can be easily spread or transmitted from person to person
  2. They result in high death rates and have the potential for major public health impact
  3. They could cause extreme concern and social disruption
  4. They require special action for public health preparedness

This section includes all Category A bioterrorism agents:

For information on Category B agents (second priority and naturally occurring infectious diseases) and Category C agents (third priority and emerging infectious diseases), see the Bioterrorism Agent Categories List.

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