Report all suspected cases of anthrax immediately to Public Health - Seattle & King County by calling 206-296-4774.

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	Epidemiology
	Microbiology and pathogenesis
	Clinical presentation
	Diagnosis
	Infection control
	Treatment and prophylaxis
	Web resources

• Soil is the natural reservoir for Bacillus anthracis, the causative agent of anthrax.
• Anthrax is predominantly a disease of animals.
• Livestock or herbivores acquire infection from consuming contaminated soil or feed.
  • Anthrax is endemic in parts of Asia, Latin America, Africa, and the Mediterranean.
  • In the U.S., natural outbreaks among animals have occurred in the Midwest, West, Texas, and Oklahoma.
• Naturally occurring illness in humans occurs following exposure to infected animals or contaminated animal products (e.g., hair, wool, hides, and consumption of undercooked meat).

Anthrax and Bioterrorism

• B. anthracis was weaponized in the former U.S. and USSR biowarfare programs.
• Anthrax spores were used to deliberately contaminate mail in 2001, resulting in 22 cases and five deaths in the Eastern U.S.
• Aerosolization is thought to be the most likely mode of dissemination of anthrax spores in a biological attack; inhalational and cutaneous anthrax are possible clinical presentations.

• B. anthracis is a large, nonmotile, spore-forming, aerobic or facultatively anaerobic, gram-positive bacillus.
• Hardy spores are resistant to drying, heat, and radiation.
• Spores are introduced to the body via the lungs, gastrointestinal tract or skin, phagocytosed by macrophages, and carried to regional lymph nodes.
• Spores can remain dormant in lymph nodes for up to 60 days before germinating into vegetative cells.
• Two binary toxins - edema toxin and lethal toxin - impair water homeostasis and lead to inflammation and tissue necrosis.

Cutaneous Anthrax:

• Accounts for 95% of naturally occurring anthrax cases.
• The incubation period is one to seven days.
• After inoculation on skin or mucous membranes, a small, sometimes pruritic, papule or vesicle develops.
• The papule ulcerates by the second day with central necrosis and drying, is surrounded by painless, non-pitting edema, and may be encircled by fine vesicles that enlarge over the next one to two days.
• An overlying, painless black eschar forms over the ulcerated area after one to two days and sloughs off after 12 to 14 days.
• Fever and malaise are common.
• Person-to-person transmission is rare.
• With appropriate antibiotics, the case-fatality rate is less than 1%.

Inhalational Anthrax:

• The incubation period is two to 43 days (usually less than one week).
• Illness may be biphasic with an initial non-specific prodrome of symptoms such as fever, malaise, fatigue, and anorexia followed by a sudden increase in fever, respiratory distress, diaphoresis, and shock, if untreated.
• Fever, sweats, cough (minimally or non-productive), nausea/vomiting, chest discomfort, and dyspnea were common in the 2001 outbreak cases.
• Bacteremia with subsequent sepsis and meningitis may develop.
• There is no known person-to-person transmission.
• The case fatality rate was 45% in the 2001 outbreak in Eastern U.S. and 86% in the 1979 Sverdlovsk outbreak.

Gastrointestinal Anthrax:

• The incubation period is one to seven days.
• Mucosal ulcer(s) develop, followed by regional lymphadenopathy.
• Fever, abdominal tenderness, diarrhea, vomiting, and headache are common.
• Pharyngeal edema, ascites, meningitis, and gastrointestinal perforation, obstruction, or hemorrhage can occur.
• There is no person-to-person transmission.
• The case-fatality rate is 25-60%.

• Gram stain and culture of lesion, blood, cerebrospinal fluid, respiratory, and gastrointestinal specimens.
• Confirmatory testing by gamma phage and direct fluorescence assay is performed at WA State Public Health Laboratory; contact Public Health - Seattle & King County for packaging and transport instructions for clinical specimens.
• Serologic testing may be used for retrospective diagnosis.
• Chest radiograph may show a widened mediastinum, hilar adenopathy, infiltrates/consolidation, or pleural effusions.
• CT scan of the chest may show abnormalities earlier than chest x-ray; hyperdense lymphadenopathy on a non-enhanced chest CT is suggestive of anthrax.
• Nasal swabs are not useful for clinical decision-making but may be useful for epidemiologic assessment.

Standard precautions are adequate.

• Soap and water is adequate for hand washing; bleach is not necessary.
• Respiratory transmission has not been documented, and therefore isolation of patients is not necessary.

Cover cutaneous lesions and treat dressings as a biohazard waste.

• First-line antibiotics for treatment or prophylaxis include ciprofloxacin and doxycycline.
• Patients with inhalational anthrax should be treated for 60 days with two or three antibiotics, initially IV, switching to oral therapy when clinically appropriate.
• Antibiotic prophylaxis should be provided for those with a suspected or known exposure to B. anthracis, as determined by public health officials, for 60 to 100 days post-exposure.
• Refer to www.bt.cdc.gov for current treatment and prophylaxis guidelines.

• Anthrax vaccine:
  • The vaccine is prepared from cell-free infiltrates of cultures of avirulent, nonencapsulated B. anthracis.
  • It is recommended as pre-exposure prophylaxis for those with occupational exposure to B. anthracis (six doses administered subcutaneously).
  • The vaccine is in limited supply and not available nor indicated for pre-exposure use in the general public.
  • Adverse reactions include local erythema, pain, fever, chills, myalgia, and nausea.
  • New vaccines are in development and alternative dosing schedules and route of administration are under investigation.

• Centers for Disease Control and Prevention
  
  • Treatment and prophylaxis (CDC)
    
    
• Infectious Disease Society of America
  
  
• Center for Biosecurity of UPMC
  
  
• Bioterrorism preparedness training modules (Univ. of WA)
  
  
• Washington Department of Health