Biological Agents of Concern

Biological agents of concern are a group of highly pathogenic bacteria, viruses, and toxins with the potential to cause significant public health impact in terms of morbidity and mortality, as well as social disruption and public panic, particularly when deployed as a biological weapon. The CDC developed a hierarchical classification system for biological agents, ranking specific agents in Categories A, B, and C, where Category A agents are the most virulent and pose the greatest public health threat. This chapter provides detailed descriptions of the Category A agents with special attention to epidemiology, pathogenesis, clinical diagnosis, treatment, and nursing care issues. Biological agents with potential for causing significant human morbidity and mortality, particularly when used as a biological weapon, are introduced. When most of us hear the term "biological weapon," we think of anthrax-laden envelopes and vials of smallpox hermetically sealed in secret laboratories. While these two well-known examples are commonly referred to when discussing bioterrorism, other very real threats are much less exotic. Bioterrorism is generally referred to as the intentional use of a biological organism or one or more of its components to cause disease, social disruption, and panic. The intentional contamination of Oregon salad bars with Salmonella typhimurium in 1984 by followers of Bhagwan Shree Rajneesh was just as much an act of biological warfare as the anthrax attacks of late 2001 (Torok et al., 1997). Potential agents of biological warfare range from the extremely rare to the very common, from Ebola virus to Escherichia coli. They vary widely in degree of infectivity, route of infection, and natural hosts. We pay special attention to those agents whose extreme pathogenicity, ease of use as a biological weapon, or potential for societal disruption place them in a distinct category in comparison with other causes of human disease. The CDC, one of the few centers in the world with the capability for research and containment of the more dangerous organisms such as smallpox, has created a hierarchy that ranks these biological agents in a system that considers their potential for causing life-threatening infection in humans, ease of dissemination or transmissibility, potential for public health impact, and requirement for special actions to facilitate public health preparedness (CDC, 2001b).