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

  • Health Care Providers: If you suspect a patient has been exposed to a biological or chemical agent please call the Office of Infectious Disease Services at (602) 364-4562
    On-call staff are available 24 hours a day, 7 days a week.


Causative Agent:
Bacillus anthracis is a spore-forming, rod-shaped gram-positive bacillus.

Routes of Transmission:
Inhalation; dermal inoculation; or ingestion through consumption of insufficiently cooked contaminated meat. Person-to-person transmission of anthrax does not occur.

Incubation Period:
The incubation period following an inhalation exposure to anthrax is 1-60 days, with most cases occurring 1-6 days after exposure. The incubation period for cutaneous anthrax is 1-5 days after inoculation. Although rare, esophageal and gastrointestinal anthrax occurs after an incubation period of 2-5 days.

Clinical Effects:
Anthrax can present in three clinical forms: inhalation, cutaneous, or gastrointestinal. Patients with inhalation anthrax will initially experience a non-specific prodrome of flu-like symptoms including fever, myalgia, headache, non-productive cough, and mild chest discomfort. Upper respiratory symptoms such as nasal congestion or rhinorrhea are not consistent with an anthrax infection. Following the prodromal period, patients may experience a brief interim improvement. Two to four days after initial symptoms, patients will experience abrupt onset of respiratory distress, high fever and hemodynamic collapse. Symptoms of respiratory stridor and dyspnea are caused by massive mediastinal lymphadenopathy, thoracic edema, and pleural effusions rather than bronchopneumonia. In its final stage, widened mediastinum is a distinguishing though inconsistent feature of anthrax infection. Approximately 50% of all cases of inhalation anthrax are accompanied by fatal hemorrhagic meningitis. Cutaneous anthrax begins with a localized pruritic papule or macule. The lesion develops into a vesicle filled with serosanguinous fluid and localized satellite vesicles may also appear. The vesicle ruptures leaving a painless, necrotic ulcer. A black eschar forms in the base of the ulcer and remains for 2-3 weeks before separating. The ulcer is usually accompanied by fever, malaise and headache. Severe local edema and lymphadenitis may be present.

Without treatment, the mortality rate for inhalation anthrax is almost 100%. Rapid treatment increase the chance of survival. In the anthrax outbreak of 2001 in the United States, six out of eleven patients with inhalational anthrax survived. Up to 20% of untreated cutaneous anthrax cases may die from septicemia; however, when appropriately treated with antibiotics, less than 1% die.

Person-to-person transmission of inhalational anthrax does not occur. Vegetative bacteria can be grown from the bullae and under the eschar of cutaneous anthrax lesions, so care must be taken with draining lesions to prevent person-to-person spread.

Primary Contamination & Methods of Dissemination:
B. anthracis (anthrax bacteria) may be delivered through aerosolization, direct dermal inoculation with spores, or contamination of food products. It is now documented that in some conditions, spores can be disseminated from an ordinarily sealed paper envelope during mechanical mail sorting activities and by simply removing the contents from a contaminated envelope.

Secondary Contamination & Persistence of Organism:
Spores can persist in the environment indefinitely. However, secondary aerosolization of spores from clothing or skin is uncommon.

Decontamination & Isolation:

  • Patients – Exposed areas of skin should be washed with soap and water after potential contact with contaminated materials. Patients with anthrax infection should be managed using standard precautions.
  • Equipment, clothing & other objects – A 0.5% hypochlorite solution is effective in cleaning the environment (1 part household bleach + 9 parts water = 0.5% solution). Contact with hypochlorite solution should be maintained for 10 minutes, to effectively kill any spores present. Sporicidal disinfectants may be effective. Contaminated clothing should be washed in soap and water, with or without bleach.

Outbreak Control:
Only those people who were exposed directly to anthrax should receive prophylaxis. There is no need to immunize or give prophylaxis to people who have later contact with anthrax-exposed individuals.

Laboratory testing:
The most useful microbiologic test is the standard blood and or wound culture, which should show growth within 24 hours. If the laboratory has been alerted to the possibility of B. anthracis (anthrax), biochemical testing and review of colonial morphology should provide a preliminary diagnosis within 12 to 24 hours. A direct fluorescent antibody test (DFA) is currently available for preliminary diagnosis at the Arizona State Health Laboratory. Laboratory confirmation for diagnosis requires an additional 1 to 2 days of testing. Sputum or nasal cultures are not useful for screening exposures.

For cutaneous lesions, collect vesicular fluid on sterile swabs. If it is in the eschar stage, use sterile swab to collect lesion material under eschar. For evaluation of inhalational anthrax, collect a routine blood culture and sputum culture.
For suspected gastrointestinal anthrax collect cultures of blood, stool, and vomitus. In addition a chest radiograph and/or chest CT scan is needed to evaluate for a widened mediastinum and pleural effusions. If symptoms of meningitis are present, cerebrospinal fluid should be cultured.

Therapeutic Treatment:
For inhalation anthrax, ciprofloxacin or doxycycline should be used for initial intravenous therapy until antimicrobial susceptibility results are known. In addition, there should be added at least one or two other antibiotics predicted to be effective, these include: vancomycin, rifampin, imipenem, chloramphenicol, clarithromycin, penicillin, or ampicillin. Although many strains of B. anthracis are sensitive to penicillin, treatment of systemic anthrax infection using penicillin alone (i.e., penicillin G or ampicillin) is not recommended until sensitivities are known.

For cutaneous anthrax infections, ciprofloxacin or doxycycline are first line therapeutic drugs. As for inhalation infection, intravenous therapy with a multidrug regimen is recommended for cutaneous anthrax if there is extensive edema, systemic involvement, or for lesions on the head and neck.

Prophylactic Treatment:
The recommended post-exposure prophylaxis for asymptomatic patients with confirmed or highly likely exposure to B. anthracis is ciprofloxacin or doxycycline. High dose penicillin (e.g., amoxicillin or penicillin VK) may be an option for antimicrobial prophylaxis when ciprofloxacin or doxycycline are contraindicated. Amoxicillin is the preferred prophylaxis for children or pregnant women if it is known that the anthrax strain is sensitive to penicillin.

Differential Diagnosis:
Anthrax should be considered in any previously healthy patient that presents with acute mediastinitis. Differential diagnoses may include bacterial pneumonias, (including pneumonic plague and tularemia pneumonia), gram negative sepsis, influenza, and other influenza-like illnesses.


  • Chin J. Control of Communicable Diseases Manual, Seventeenth Edition, American Public Health Association; 2000.
  • Dennis DT, Inglesby TV, Henderson DA, et al. Anthrax as a Biological Weapon, 2002: Updated Recommendations for Management. JAMA. 2002; 287: 2236-2252.
  • Inglesby TV, Henderson DA, Bartlett JG, et al. Anthrax as a Biological Weapon: Medical and Public Health Management, JAMA. 1999; 281: 1735-1745.
  • 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; 2001:14-18
  • Friedlander AM. Anthrax. 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; 1997:467-478.

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