ABSTRACT: The 2001 anthrax attack demonstrated the United States' vulnerability to bioterrorism. Governmental and public health agencies are preparing for the enormous logistical challenges required for a response to a large-scale bioterrorist attack. These include the stockpiling and distribution of antibiotics and vaccines for prophylaxis and treatment of exposed populations. Given that untreated inhalational anthrax is rapidly fatal, early identification and timely initiation of appropriate therapy are essential. The prodromal phase of illness is characterized by flu-like symptoms, such as cough, fever, and fatigue, followed by respiratory distress and shock. Chest radiographic findings include pleural effusions and widening of the mediastinum.
KEY WORDS: Anthrax, Bioterrrorism
The 2001 anthrax outbreak in the United States and the 1979 outbreak in Sverdlovsk, Russia, demonstrated that inhalational anthrax is no longer only of historical interest. (1,2) Unfortunately, the United States is still a possible target for future bioterrorist attacks. The US Commission on National Security, headed by former Senators Rudman and Hart, concluded that the United States is vulnerable to attack and cited biological weapons, such as anthrax, as "the most likely choice and means for disaffected states and groups in the 21st century." (3) There is growing evidence that Al Qaeda is attempting to "produce biological weapons, such as anthrax [to be used] on American soil." (4)
When untreated, inhalational anthrax results in a rapidly fatal illness --usually within 5 days of symptom onset. (5) Thus, it is imperative that health care providers be aware of the clinical signs and symptoms associated with inhalational anthrax, for timely diagnosis and initiation of lifesaving therapy.
In this article, we describe the history of zoonotic, occupational, and bioterrorism-related anthrax exposures. Then, we review the clinical course of inhalational anthrax. In a coming issue of The Journal of Respiratory Diseases, we will review the guidelines for treatment.
Microbiology and pathogenesis
The aerobic, gram-positive, non-motile, spore-forming bacterium Bacillus anthracis (size: 1 to 1.5 [micro]m by 3 to 10 [micro]m) causes acute infectious diseases in humans and animals (Figure 1). (6) Viable anthrax spores resist environmental degradation and can exist in the soil for decades. (7) Infection ensues once the spores introduced to the blood and tissue of living hosts germinate into vegetative bacilli.
The 3 generally accepted routes of B anthracis infection in humans are cutaneous, GI (lower or upper/ pharyngeal), and inhalational. (8) Although several cases of primary anthrax meningioencephalitis have been described, (9) these cases are likely the result of an unrecognized lower respiratory tract (10) or a transethmoidal port of entry. (11-13)
Inhalational anthrax is thought to occur when anthrax particles smaller than 5 [micro]m reach the lower respiratory tract (the alveoli) where alveolar macrophages phagocytize and transport these spores to the hilar and mediastinal lymph nodes. (6,14) The spores germinate and produce bacterial toxins that cause hemorrhage, edema, and necrosis. (15) An initial prodromal syndrome is characterized by flu-like and respiratory symptoms, including fever, cough, and dyspnea. (5,16) A poorly recognized upper airway form of inhalational anthrax, presenting with primarily nonpulmonary symptoms, also...