The U.S. public health system and primary healthcare providers must be prepared to address various biological agents, including pathogens that are rarely seen in the United States.

Category A Diseases/Agents

High-priority agents include organisms that 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 major public health impact;
might cause public panic and social disruption; and
require special action for public health preparedness.

Category B Diseases/Agents

Second highest priority agents include those that

are moderately easy to disseminate;
result in moderate morbidity rates and low mortality rates; and
require specific enhancements of CDC's diagnostic capacity and enhanced disease surveillance.

Category C Diseases/Agents

Third highest priority agents include emerging pathogens that could be engineered for mass dissemination in the future because of

availability;
ease of production and dissemination; and
potential for high morbidity and mortality rates and major health impact.

For more information on the agent/disease selection and prioritization process, see Rotz LD, Khan AS, Lillibridge SR, et all. Public health assessment of potential biological terrorism agents. Emerg Infect Dis 2002; 8(2):225-30. http://www.cdc.gov/ncidod/eid/vol8no2/01-0164.htm