Bioterrorism

Profiles for Health Care Workers (Fact Sheets) - "A" Agents

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Anthrax | Botulism | Plague | Smallpox | Tularemia | Viral Hemorrhagic Fevers

Plague

Causative Agent:
Gram-negative bacillus Yersinia pestis.

Routes of Exposure:
Inhalation, fleabite, and direct contact with infected blood and tissues.

Infective Dose & Infectivity:
10-500 organisms Incubation Period: The incubation period for pulmonary exposure ranges from 1 to 6 days with an average of 2-4 days.

Clinical Effects:
Onset of pneumonic plague is acute and often fulminant. The presentation includes high fever, cough, chest pain, malaise, hemoptysis, and muco-purulent or watery sputum with gram-negative rods on gram stain. Patients commonly show evidence of bronchopneumonia. The pneumonia progresses rapidly, resulting in dyspnea, stridor and cyanosis. Gastrointestinal symptoms including nausea, vomiting, diarrhea and abdominal pain might also be present. Buboes (regional lymphadenopathy) are rarely seen. Other advanced signs of pneumonic plague include respiratory failure, circulatory collapse, and bleeding diathesis.

Lethality:
The mortality rate of untreated pneumonic plague usually is 90-100%. However, with prompt appropriate treatment, the mortality rate drops to 5% or less.

Transmissibility (person to person):
Person-to-person transmission occurs via respiratory droplets.

Primary Contamination & Methods of Dissemination:
Dissemination of plague as a biological weapon would most likely be through aerosolization.

Secondary Contamination & Persistence of organism:
Y. pestis is very sensitive to sunlight and heat and does not survive long outside of the host. Therefore, secondary contamination is not a concern.

Decontamination & Isolation:

  • Patients – Patients with suspected pneumonic plague should be managed with droplet precautions. Plague patients without pneumonia require only standard precautions. Drainage from buboes should be considered infectious and treated with appropriate personal protective equipment (e.g. gloves when touching drainage, gowns if clothes could be contaminated).
  • Equipment & other objects – Environmental decontamination can be done using a 0.5% hypochlorite solution (1 part household bleach + 9 parts water = 0.5% solution), prior to normal cleaning or washing.
  • Outbreak control – All patients with pneumonic plague should be in droplet isolation for the first 48 hours after the initiation of treatment. This means that a healthcare worker should use a surgical mask within 3 feet of the patient. Those who have been in household or face-to-face contact with patients with pneumonic plague should be given antibiotic prophylaxis and placed under fever surveillance for 7 days.

Laboratory Testing:
A presumptive diagnosis can be made microscopically by identification of the gram-negative coccobacillus with safety-pin bipolar staining in Gram or Wayson’s stained smears from peripheral blood, sputum, or cerebrospinal fluids sample. When available, immunofluorescent staining is very useful.

  • Cultures of blood, sputum, buboes, and CSF, should be processed on blood agar, MacConkey agar or infusion broth. The organism grows slowly at normal incubation temperatures, and may be misidentified by automated systems because of delayed biochemical reactions. Confirmation of organism is done by DFA, phage typing, and/or PCR.
  • Antibody response test - A four-fold rise in antibody titer by ELISA or passive hemagglutination in patient serum is also diagnostic. Therapeutic Treatment: Historically, the treatment of choice for bubonic, septicemic, and pneumonic plague has been streptomycin. However, since streptomycin is no longer readily available, gentamicin appears just as effective. Doxycycline or ciprofloxacin* are alternative antibiotics. Once the patient is stable, an effectice oral antibiotic can be used to complete the course of therapy. IV chloramphenicol is the drug of choice for plague meningitis.

Prophylactic Treatment:
Because of oral administration and relative lack of toxicity, the antibiotic for prophylaxis or for use in face-to-face contacts of patients with pneumonic plague is doxycycline.

Differential diagnosis:
For pneumonic plague the differential diagnoses should include any acute pneumonia, tularemia, hantavirus pulmonary syndrome, and anthrax.

References:

  • Chin J. Control of Communicable Diseases Manual, Seventeenth Edition, American Public Health Association; 2000.
  • Inglesby TV, Dennis DT, Henderson DA, et al. Plague as a Biological Weapon: Medical and Public Health Management. JAMA. 2000; 283: 2281-2290.
  • Kortepeter M, Christopher G, Cieslak T, et al. Medical Management of Biological Casualties Handbook, U.S. Army Medical Research Institute of Infectious Diseases, U.S. Department of Defense; 2001:28-32
  • McGovern TW, Friedlander AM. Plague. In: Zajtchuk R, Bellamy RF, eds. Medical Aspects of Chemical and Biological Warfare. Washington, DC: Office of the Surgeon General, U.S. Department of the Army; 1997: 479-502.
  • Dennis DT. Plague. In: Conn HF, ed. Conn’s Current Therapy. Philadelphia: WB Saunders, 1996: 124-126.

*Ciprofloxicin does not have an FDA approved indication for treatment of plague.


Find the PDF version of this Fact Sheet in the Zebra Manual.