·        Caused by Bacillus anthracis, a large, encapsulated, gram-positive, aerobic, non-motile, spore-forming bacillus

·        Transmission to humans usually occurs through occupational contact with infected animals or animal products

·        Naturally acquired anthrax in humans most commonly involves the skin (cutaneous anthrax); inhalation anthrax and gastrointestinal (GI) anthrax are rare

·        B. anthracis is considered one of the most likely biological warfare or terrorist threat agents

·        The most likely outcome of an intentional (bioterrorist) exposure involving anthrax would be cases of inhalation anthrax, caused by inhaling aerosolized spores

·        Person-to-person transmission does NOT occur with inhalation or GI anthrax

Inhalation Anthrax

Incubation: 1-5 days (may be as long as 60 days with low inoculum exposures)

Sign and Symptoms:            Typically a bi-phasic illness:

  • Initial Phase: Characterized by flu-like symptoms: Low grade fever, non-productive cough, malaise, fatigue, myalgias, mild chest discomfort. Rhonchi may be present, otherwise normal exam.

  • Acute Phase: Develops 1-5 days after initial symptoms. May be preceded by <1-3 days of improvement. Characterized by abrupt development of  severe respiratory distress with dyspnea, stridor, cyanosis, and high fever. Shock and death usually follow within 24-36 hours after onset of respiratory distress. The average interval between onset of initial phase and death is 3 days.

CXR:      Mediastinal widening, often with pleural effusion, but usually no infiltrates (highly suspicious for anthrax)

·        Autopsy Clues: Hemorrhagic necrotizing mediastinitis and thoracic hemorrhagic necrotizing lymphadenitis. Hemorrhagic meningitis may also be present.  

CUTANEOUS ANTHRAX (a possible, though unlikely outcome of a terrorist release of B. anthracis)

  • Local skin involvement after direct contact with spores or bacilli

  • Commonly seen on exposed areas: face, neck, forearms, hands

  • Localized itching, followed by a papular lesion that turns vesicular, followed by development of a black eschar within 7-10 days of onset of the initial lesion

  • Usually non-fatal if treated with appropriate antibiotics for 7-10 days

  • Wound or wound drainage may be contagious (direct contact): follow standard wound precautions

GASTROINTESTINAL ANTHRAX (very unlikely outcome of a terrorist release of B. anthracis)

  • Abdominal pain, nausea, vomiting, and fever following ingestion of contaminated food, usually meat

  • Bloody diarrhea, hematemesis

  • Gram-positive bacilli on blood or stool culture, usually after 2-3 days of illness

  • Usually fatal after progression to septicemia

Treatment is the same as for inhalation anthrax (see Inhalation Anthrax Treatment Protocol)


Laboratory Clues to Bacillus anthracis:

  • Peripheral blood smear: gram-positive bacilli on an unspun smear.

  • Microbiology: Aerobic blood culture growth of large, gram-positive bacilli with preliminary identification of Bacillus species

Laboratory Confirmation of Diagnosis

  • Should be performed by the State Department of Health (DOH) Public Health Laboratory

  • Appropriate clinical samples for testing at DOH include: blood (most important); pleural fluid and CSF may be helpful

  • Transport and packaging of clinical specimens must be coordinated with local and State health departments 

  • DOH has the capacity to report some preliminary results within 2 to 4 hours


  • Early (during the initial phase) antibiotic treatment is essential. Mortality may still be high (~90%) after the onset of symptoms even with treatment

  • Natural strains of anthrax are resistant to extended-spectrum cephalosporins, sulfamethoxazole, and trimethoprim: these should not be used for treating (or prophylaxis against) anthrax

  • Physicians may be asked to get an informed consent signed for administration of certain medications supplied by the National Pharmaceutical Stockpile (NPS)       


  • Antibiotic prophylaxis should be initiated when exposure to aerosolized anthrax spores is suspected

  • Initiation of prophylaxis, especially in children, should be coordinated with the local health jurisdiction or the DOH

  • Prophylaxis should continue for at least 60 days if the exposure is confirmed

  • Physicians may be asked to get an informed consent signed for administration of certain medications supplied by the National Pharmaceutical Stockpile (NPS)


Therapy for Patients With Clinically Evident Inhalational Anthrax Infection in the Contained Casualty Setting


Initial Therapy2

Optimal Therapy if Susceptible





Ciprofloxacin* 400 mg IV every 12 h


Penicillin G* 4 MU IV every 4 h

Doxycycline* 100 mg IV every 12 h5



60 days




Ciprofloxacin* 20-30 mg/kg IV divided into 2 daily doses

(max daily dose 1 g/day)


Age<12 y: penicillin G*, 50,000 U/kg IV every 6 h

Age³12 y: penicillin G*, 4 MU every 4 h


60 days

Therapy for Patients with Clinically Evident Anthrax Infection in the Mass Casualty Setting or for Postexposure Prophylaxis


Initial Therapy2

Optimal Therapy if Susceptible





Ciprofloxacin* 500 mg PO every 12 h


Amoxicillin, 500 mg every 8 h

Doxycycline*, 100 mg PO every 12 h7


60 days




Ciprofloxacin* 20-30 mg/kg PO divided into 2 daily doses

(max daily dose 1 g/day)


Weight ³ 20kg: amoxicillin, 500 mg PO every 8 h

Weight <20 kg: amoxicillin, 40 mg/kg divided into 3 doses to be taken every 8 h



60 days

Pregnant Women

Ciprofloxacin* 500 mg PO every 12 h

Amoxicillin 500 mg PO every 8 h

60 days

1. Adapted from recommendations of the Working Group on Civilian Biodefense, and not necessarily approved by the Food and Drug Administration.  In non-bioterrorism situations, routine treatment guidelines should be followed.  For explanations and further discussion, see Inglesby et al. Anthrax as a Biological Weapon: Medical and Public Health Management JAMA. 1999; 281(18): 1735-1745.

2. In vitro studies suggest ofloxacin, 400 mg IV or PO every 12 hours, or levofloxacin, 500 mg IV or PO every 24 hours, could be substituted for ciprofloxacin.

3. Oral antibiotics should be substituted for IV antibiotics as soon as clinical condition improves.

4. Includes pregnant women and immunosuppressed individuals.

5. In vitro studies suggest tetracycline could be substituted for doxycycline.

6. Doxycycline could also be used. For children >45 kg, use adult dosage.  For children £ 45kg use 2.5 mg/kg doxycycline IV or PO every 12 h.

7. In vitro studies suggest tetracycline, 500 mg PO every 6 hours, could be substituted for doxycycline.

8.  Includes immunosuppressed adults

* indicates medications which will be supplied as part of the NPS maintained at the CDC.


  • An inactivated cell-free vaccine that is available only to the military and those at occupational risk

  • Is only licensed for use in healthy adults aged 18-65

  • Anthrax vaccine supplies are very limited, however, and it is unlikely that the vaccine will be available for the general public in the future. 

  • If vaccine is not available, antibiotic treatment should be continued for at least 30 days and possibly up to 60 days

Infection Control

  • Standard (Universal) Precautions for care and transport of patients and during post-mortem care

  • Wound precautions for patients with cutaneous anthrax

  • Isolation of patients is NOT necessary; however, the following extra precautions are advised:

  • After an invasive procedure, instruments used should be autoclaved

  • Contaminated clothing/bedding should be placed in labeled, plastic bags for later incineration or steam sterilization

  • Spills of potentially infected body fluid or tissue

-     Gently cover, then liberally apply 0.5% hypochlorite ( a 1:10 dilution of household bleach)

-      Let sit for at least 20 minutes before cleaning up (work from perimeter to center)

-      Any materials used in the clean-up must be autoclaved or incinerated

-      Rinse off the concentrated bleach to avoid its caustic effects

Contamination of personnel

-         Remove outer clothing carefully where spill occurred and place in a labeled, plastic bag

-         Remove rest of clothing in the locker room and place in a labeled, plastic bag

-         Shower thoroughly with soap and water

·        If exposure to contaminated sharps occurs:

  • Follow standard reporting procedures for sharps exposures

  • Thoroughly irrigate site with soap and water and apply a disinfectant solution such as hypochlorite solution.  DO NOT SCRUB AREA.

  • Promptly begin therapy for cutaneous anthrax

  • Recommended treatment for cutaneous exposure: prophylaxis with ciprofloxacin 500 mg PO BID x 7-10 days

  • Notify the DOH

Decontamination of environment

  • Use a decontamination solution , 0.5% hypochlorite ( a 1:10 dilution of household bleach) for surfaces

  • Let sit for at least 20 minutes before cleaning up (work from perimeter to center)

  • Routinely clean non-sterilizable equipment with a sterilizing solution

  • Cremation should be considered due to potential risks associated with embalming