The pathogens or toxins that cause anthrax, plague, tularemia, Brucellosis, viral encephalitis, smallpox, botulism, and Staphylococcal enterotoxemia have been weaponized or considered for use in biological weapons programs. Although a certain number of cases of these diseases (except smallpox) occur naturally in the U.S. each year, they still should be evaluated carefully with a certain index of suspicion. Some of these diseases display distinct clinical appearances and pathology depending upon the route of exposure. Analysis of this information may be valuable in suggesting a source for the outbreak and whether or not foul play may be involved.
An excellent review of the diagnosis and management of patients exposed to biological warfare agents was recently published; the reader is referred to that publication for additional information56. The present discussion will focus on specific aspects of clinical disease that point to intentional misuse.
Anthrax has three clinical presentations: cutaneous, gastrointestinal, and inhalational. Inhalational anthrax begins with fever, malaise, nonproductive cough, and chest discomfort and progresses to severe respiratory distress, bac-teremia, septic shock, metastatic infection, and death. Physical findings are nonspecific. Chest radiographs typically show a widened mediastinum57. Inhalational anthrax, as found in Sverdlovsk and the October 2001 postal attacks in the U.S., is highly indicative of deliberate exposure. Although gastrointestinal anthrax occurs in countries lacking well-developed meat inspection systems, in the U.S. it is rare and would be considered suspicious.
There are three clinical presentations of plague-bubonic, primary septicemic, and pneumonic. Patients with pneumonia due to Yersinia pestis present with high fever, headache, myalgia, and productive cough with bloody sputum, which progresses rapidly to sepsis58. Plague has been endemic in the western U.S. since 1900, with 5-15 cases of human disease occurring each year; however, only 2% of plague has been pneumonic. Therefore pneumonic plague in the U.S. would raise the suspicion of an intentional event.
Tularemia presents as ulcero-glandular disease when the initiating event is penetration through the skin or mucous membranes. Typhoidal and septicemic disease, which presents with fever and weight loss, usually develops after inhalation of infectious aerosols. Pneumonia occurs with either form, but more likely follows inhalation59. Therefore, a tularemia outbreak with a high inci dence of pneumonic disease should be investigated with intentional misuse in mind.
Patients with inhalation-induced Staphylococcal B enterotoxemia have difficult breathing and chest pain: in severe cases there may be pulmonary edema progressing to adult respiratory distress syndrome.56 While some cases of inhalation-induced disease have gastrointestinal symptoms, naturally occurring cases of staphylococcal food poisoning cases do not present with pulmonary signs or symptoms.
Ricin induces severe pulmonary disease after inhalation exposure60 as contrasted with severe gastrointestinal signs of nausea, vomiting, diarrhea, and rectal hemorrhage56 after oral administration. The signs and symptoms of Botulinum intoxication and Brucella infection do not differ with route of administration.56
When traditional pathogens are deliberately used in a typical route of exposure, for example when Rajneesh cult members contaminated a salad bar with Salmonella, the clinical syndrome induced by misuse may present an identical clinical picture to naturally occurring disease.16
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