Site(s) of Infection; Transmission Mode

Cutaneous and inhalation disease have occurred in past bioterrorist incidents

Cutaneous (contact with spores).

Respiratory Tract: (inhalation of spores).

Gastrointestinal Tract: (ingestion of spores – rare).

Comment: Spores can be inhaled into the lower respiratory tract. The infectious dose of B. anthracis in humans by any route is not precisely known. In primates, the LD50 (i.e., the dose required to kill 50% of animals) for an aerosol challenge with B. anthracis is estimated to be 8,000–50,000 spores; the infectious dose may be as low as 1-3 spores.

Cutaneous: 1 to12 days.

Respiratory Tract: Usually 1 to 7 days but up to 43 days reported.

Gastrointestinal Tract: 15-72 hours.

Clinical

Features

Cutaneous: Painless, reddish papule, which develops a central vesicle or bulla in 1-2 days; over next 3-7 days lesion becomes pustular, and then necrotic, with black eschar; extensive surrounding edema.

Respiratory Tract: initial flu-like illness for 1-3 days with headache, fever, malaise, cough; by day 4 severe dyspnea and shock, and is usually fatal (85%-90% if untreated; meningitis in 50% of Respiratory Tract cases.

Gastrointestinal Tract: if intestinal form, necrotic, ulcerated edematous lesions develop in intestines with fever, nausea and vomiting, progression to hematemesis and bloody diarrhea; 25-60% fatal

Cutaneous: Swabs of lesion (under eschar) for immunohistochemistry, polymerase chain reaction and culture; punch biopsy for immunohistochemistry, polymerase chain reaction and culture; vesicular fluid aspirate for Gram stain and culture; blood culture if systemic symptoms; acute and convalescent sera for ELISA serology.

Respiratory Tract: Chest X-ray or CT scan demonstrating wide mediastinal widening and/or pleural effusion, hilar abnormalities; blood for culture and polymerase chain reaction; pleural effusion for culture, polymerase chain reaction and immunohistochemistry; cerebrospinal fluid if meningeal signs present for immunohistochemistry, polymerase chain reaction and culture; acute and convalescent sera for ELISA serology; pleural and/or bronchial biopsies immunohistochemistry.

Gastrointestinal Tract: blood and ascites fluid, stool samples, rectal swabs, and swabs of oropharyngeal lesions if present for culture, polymerase chain reaction and immunohistochemistry.

Cutaneous: Person-to-person transmission from contact with lesion of untreated patient possible, but extremely rare.

Respiratory Tract and Gastrointestinal Tract:Person-to-person transmission does not occur.

Aerosolized powder, environmental exposures: Highly infectious if aerosolized.

Cutaneous: Standard Precautions; Contact Precautions if uncontained copious drainage.

Respiratory Tract and Gastrointestinal Tract: Standard Precautions.

Aerosolized powder, environmental exposures: Respirator (N95 mask or Powered Air Purifying Respirators), protective clothing; decontamination of persons with powder on them (Notice to Readers: Occupational Health Guidelines for Remediation Workers at Bacillus anthracis-Contaminated Sites — United States, 2001–2002).

Hand hygiene: Handwashing for 30-60 seconds with soap and water or 2% chlorhexidene gluconate after spore contact (alcohol handrubs inactive against spores [Weber DJ JAMA 2003; 289:1274]).

Post-exposure prophylaxis following environmental exposure: 60 days of antimicrobials (either doxycycline, ciprofloxacin, or levofloxacin) and post-exposure vaccine under IND.

Gastrointestinal Tract: Ingestion of toxin-containing food.

Respiratory Tract: Inhalation of toxin containing aerosol cause disease.

Comment: Toxin ingested or potentially delivered by aerosol in bioterrorist incidents. LD50 (lethal dose for 50% of experimental animals) for type A is 0.001 μg/ml/kg.

Hemorrhagic fever specific barrier precautions: If disease is believed to be related to intentional release of a bioweapon, epidemiology of transmission is unpredictable pending observation of disease transmission. Until the nature of the pathogen is understood and its transmission pattern confirmed, Standard, Contact and Airborne Precautions should be used. Once the pathogen is characterized, if the epidemiology of transmission is consistent with natural disease, Droplet Precautions can be substituted for Airborne Precautions. Emphasize:

1. use of sharps safety devices and safe work practices;
2. hand hygiene;
3. barrier protection against blood and body fluids upon entry into room (single gloves and fluid- resistant or impermeable gown, face/eye protection with masks, goggles or face shields); and
4. appropriate waste handling.

Use N95 or higher respirators when performing aerosol-generating procedures. In settings where AIIRs are unavailable or the large numbers of patients cannot be accommodated by existing AIIRs, observe Droplet Precautions (plus Standard Precautions and Contact Precautions) and segregate patients from those not suspected of VHF infection. Limit blooddraws to those essential to care. See text for discussion and Appendix A for recommendations for naturally occurring VHFs.

Respiratory Tract: Inhalation of respiratory droplets.

Comment: Pneumonic plague most likely to occur if used as a biological weapon, but some cases of bubonic and primary septicemia may also occur. Infective dose 100 to 500 bacteria.

Standard Precautions, Droplet Precautions until patients have received 48 hours of appropriate therapy.

Chemoprophylaxis: Consider antibiotic prophylaxis for HCWs with close contact exposure.

Respiratory Tract Inhalation of droplet or, rarely, aerosols; and skin lesions (contact with virus).

Comment: If used as a biological weapon, natural disease, which has not occurred since 1977, will likely result.

Combined use of Standard, Contact, and Airborne Precautions until all scabs have separated (3-4 weeks).

Transmission by the airborne route is a rare event; Airborne Precautions is recommended when possible, but in the event of mass exposures, barrier precautions and containment within a designated area are most important.^{204, 212}

Only immune HCWs to care for pts; post-exposure vaccine within 4 days.

Vaccinia: HCWs cover vaccination site with gauze and semi-permeable dressing until scab separates (≥21 days). Observe hand hygiene.

Adverse events with virus-containing lesions: Standard plus Contact Precautions until all lesions crusted.

Vaccinia adverse events with lesions containing infectious virus include inadvertent autoinoculation, ocular lesions (blepharitis, conjunctivitis), generalized vaccinia, progressive vaccinia, eczema vaccinatum; bacterial superinfection also requires addition of contact precautions if exudates cannot be contained. ^{216, 217}

Respiratory Tract: Inhalation of aerosolized bacteria. Gastrointestinal Tract: Ingestion of food or drink contaminated with aerosolized bacteria.

Comment: Pneumonic or typhoidal disease likely to occur after bioterrorist event using aerosol delivery. Infective dose 10-50 bacteria.

Pneumonic: malaise, cough, sputum production, dyspnea.

Typhoidal: fever, prostration, weight loss and frequently an associated pneumonia.

Person-to-person spread is rare.

Laboratory workers who encounter/handle cultures of this organism are at high risk for disease if exposed.