Infection Control Considerations for High-Priority (CDC Category A) Diseases that May Result from Bioterrorist Attacks or are Considered to be Bioterrorist Threats

Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings (2007)

Appendix A: Table 3.

[This link is no longer active: Similar information may be found at CDC Bioterrorism Agents/Diseases. Accessed May 2016.]

Format Change [February 2017]

Update or clarification r17The format of this section was changed to improve readability and accessibility. The content is unchanged.


Table 3A. Anthrax

Two column table listing anthrax characteristics and information on each.
Characteristics Additional Information
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.

Incubation Period Cutaneous: 1 to12 days.Respiratory Tract: Usually 1 to 7 days but up to 43 days reported.

Gastrointestinal Tract: 15-72 hours.



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

Diagnosis 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.

Infectivity 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.

Recommended Precautions 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.

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Table 3B. Botulism

Two column table listing Botulism characteristics and information on each.
Characteristics Additional Information
Site(s) of Infection; Transmission Mode 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.

Incubation Period 1-5 days.
Clinical Features Ptosis, generalized weakness, dizziness, dry mouth and throat, blurred vision, diplopia, dysarthria, dysphonia, and dysphagia followed by symmetrical descending paralysis and respiratory failure.
Diagnosis Clinical diagnosis; identification of toxin in stool, serology unless toxin-containing material available for toxin neutralization bioassays.
Infectivity Not transmitted from person to person. Exposure to toxin necessary for disease.
Recommended Precautions Standard Precautions.

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Ebola Hemorrhagic Fever

Ebola Virus Disease for Healthcare Workers [2014]

Update or clarification r8 Update: Recommendations for healthcare workers can be found at Ebola For Clinicians.

Table 3C. Ebola Hemorrhagic Fever

Ebola characteristics and information.
Characteristics Additional Information
Site(s) of Infection; Transmission Mode As a rule infection develops after exposure of mucous membranes or respiratory tract, or through broken skin or percutaneous injury.
Incubation Period 2-19 days, usually 5-10 days.
Clinical Features Febrile illnesses with malaise, myalgias, headache, vomiting and diarrhea that are rapidly complicated by hypotension, shock, and hemorrhagic features. Massive hemorrhage in < 50% pts.
Diagnosis Etiologic diagnosis can be made using respiratory tract-polymerase chain reaction, serologic detection of antibody and antigen, pathologic assessment with immunohistochemistry and viral culture with EM confirmation of morphology.
Infectivity Person-to-person transmission primarily occurs through unprotected contact with blood and body fluids; percutaneous injuries (e.g., needlestick) associated with a high rate of transmission; transmission in healthcare settings has been reported but is prevented by use of barrier precautions.
Recommended Precautions 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.

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Pneumonic plague is not as contagious as is often thought. Historical accounts and contemporary evidence indicate that persons with plague usually transmit the infection only when the disease is in the end stage. These persons cough copious amounts of bloody sputum that contains many plague bacteria. Patients in the early stage of primary pneumonic plague (approximately the first 20–24 h) apparently pose little risk [1, 2]. Antibiotic medication rapidly clears the sputum of plague bacilli, so that a patient generally is not infective within hours after initiation of effective antibiotic treatment [3]. This means that in modern times many patients will never reach a stage where they pose a significant risk to others. Even in the end stage of disease, transmission only occurs after close contact. Simple protective measures, such as wearing masks, good hygiene, and avoiding close contact, have been effective to interrupt transmission during many pneumonic plague outbreaks [2]. In the United States, the last known cases of person to person transmission of pneumonic plague occurred in 1925 [2].

Table 3D. Plague

plague characteristics and information.
Characteristics Additional Information
Site(s) of Infection; Transmission Mode 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.
Incubation Period 1 to 6, usually 2 to 3 days.
Clinical Features Pneumonic: fever, chills, headache, cough, dyspnea, rapid progression of weakness, and in a later stage hemoptysis, circulatory collapse, and bleeding diathesis.
Diagnosis Presumptive diagnosis from Gram stain or Wayson stain of sputum, blood, or lymph node aspirate; definitive diagnosis from cultures of same material, or paired acute/convalescent serology.
Infectivity Person-to-person transmission occurs via respiratory droplets risk of transmission is low during first 20-24 hours of illness and requires close contact. Respiratory secretions probably are not infectious within a few hours after initiation of appropriate therapy.
Recommended Precautions Standard Precautions, Droplet Precautions until patients have received 48 hours of appropriate therapy.

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

1 Wu L-T. A treatise on pneumonic plague. Geneva: League of Nations, 1926. III. Health.

2 Kool JL. Risk of person to person transmission of pneumonic plague. Clinical Infectious Diseases, 2005; 40 (8): 1166-1172

3 Butler TC. Plague and other Yersinia infections. In: Greenough WB, ed. Current topics in infectious disease. New York: Plenum Medical Book Company,1983.

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Table 3E. Smallpox

smallpox characteristics and information.
Characteristics Additional Information
Site(s) of Infection; Transmission Mode 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.
Incubation Period 7 to 19 days (mean 12 days).
Clinical Features Fever, malaise, backache, headache, and often vomiting for 2-3 days; then generalized papular or maculopapular rash (more on face and extremities), which becomes vesicular (on day 4 or 5) and then pustular; lesions all in same stage.
Diagnosis Electron microscopy of vesicular fluid or culture of vesicular fluid by WHO approved laboratory (CDC); detection by polymerase chain reaction available only in select LRN labs, CDC and USAMRID.
Infectivity Secondary attack rates up to 50% in unvaccinated persons; infected persons may transmit disease from time rash appears until all lesions have crusted over (about 3 weeks); greatest infectivity during first 10 days of rash.
Recommended Precautions 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

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Table 3F. Tularemia

Tularemia characteristics and information.
Characteristics Additional Information
Site(s) of Infection; Transmission Mode 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.
Incubation Period 2 to 10 days, usually 3 to 5 days.
Clinical Features Pneumonic: malaise, cough, sputum production, dyspnea.

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

Diagnosis Diagnosis usually made with serology on acute and convalescent serum specimens; bacterium can be detected by polymerase chain reaction (LRN) or isolated from blood and other body fluids on cysteine-enriched media or mouse inoculation.
Infectivity Person-to-person spread is rare.

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

Recommended Precautions Standard Precautions

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