David A. Relman, MD

Plague is caused by Yersiniapestis, a gram-negative, nonmotile,nonsporulating bacillus.It is a zoonotic disease, and rodentsare the primary reservoir.Plague can present as bubonic,pneumonic, or primary septicemic disease.Y pestis is usually transmitted tohumans via the bites of infected fleas,causing the bubonic form of the disease.Primary septicemic and secondarypneumonic disease are muchless common. Primary pneumonicdisease results from aerosol exposureto an infected animal or human withplague pneumonia; however, it too hasbecome uncommon as a natural event.Nonetheless, primary pneumonicplague, or a similar illness, is the mostlikely manifestation following a bioterroristattack.1,2 Despite the substantialinvestment by the former Soviet Unionin this agent as a potential weapon,there is little experience from whichto predict the clinical consequencesof intentional aerosolization of thisorganism.

Francisella tularensis is anonsporulating, nonmotile,aerobic gram-negative coccobacillusthat is usually transmittedto humans frominfected rabbits and other small animalsvia ticks, fleas, or deer flies orby direct contact

In 1978, a ricin-filled pellet-which was injected with aspring-loaded device disguised in an umbrella-wasused to assassinate Bulgarian defector Georgi Markov.A similar device was employed unsuccessfully against asecond defector in the same year.1

The last naturally occurringcase of smallpox was reportedin Somalia in October 1977.Despite the eradication ofsmallpox, the causative agent,variola virus, remains in existence.1,2

Until recently, the specter of biologicwarfare or bioterrorism was infrequentlydiscussed by most physicians,despite the attention it had receivedfrom novelists, screenplay writers,politicians, and military defense strategists.Thankfully, most physicians havestill never encountered the malevolentuse of biologic agents, nor have theytreated a victim of a biologic attack. Infact, despite their occasional occurrencein a “natural setting,” as well asin recent events, clinical cases involvingany of the classic biothreat agentsare rarely encountered even by mostinfectious disease physicians.