Table 3.
Infection control considerations for high-priority (CDC category A) diseases that may result from bioterrorist attacks or are considered bioterrorist threats (see http://www.bt.cdc.gov)
| Disease | Anthrax |
|---|---|
| Site(s) of infection; transmission mode | Cutaneous (contact with spores); RT (inhalation of spores); GIT (ingestion of spores [rare]) |
| Cutaneous and inhalation disease have occurred in past bioterrorist incidents | Comment: Spores can be inhaled into the lower respiratory tract. The infectious dose of Bacillus anthracis in humans by any route is not precisely known. In primates, the LD50 for an aerosol challenge with B anthracis is estimated to be 8,000 to 50,000 spores; the infectious dose may be as low as 1 to 3 spores. |
| Incubation period | Cutaneous: 1 to 12 days; RT: Usually 1 to 7 days, but up to 43 days reported; GIT: 15 to 72 hours |
| Clinical features | Cutaneous: Painless, reddish papule that develops a central vesicle or bulla in 1 to 2 days; over the next 3 to 7 days, the lesion becomes pustular and then necrotic, with black eschar and extensive surrounding edema |
| RT: Initial flu-like illness for 1 to 3 days with headache, fever, malaise, cough; by day 4, severe dyspnea and shock. Usually fatal (85% to 90%) if untreated; meningitis develops in 50% of RT cases. | |
| GIT: In intestinal form, necrotic, ulcerated edematous lesions develop in intestines with fever, nausea, and vomiting and progression to hematemesis and bloody diarrhea; 25% to 60% mortality | |
| Diagnosis | Cutaneous: Swabs of lesion (under eschar) for IHC, PCR, and culture; punch biopsy for IHC, PCR, and culture; vesicular fluid aspirate for Gram's stain and culture; blood culture if systemic symptoms present; acute and convalescent sera for ELISA serology |
| RT: CXR or CT demonstrating wide mediastinal widening and/or pleural effusion and hilar abnormalities; blood for culture and PCR; pleural effusion for culture, PCR, and IHC; CSF (if meningeal signs present) for IHC, PCR, and culture; acute and convalescent sera for ELISA serology; pleural and/or bronchial biopsy specimens for IHC | |
| GIT: Blood and ascites fluid, stool samples, rectal swabs, and swabs of oropharyngeal lesions, if present, for culture, PCR, and IHC | |
| Infectivity | Cutaneous: Person-to-person transmission from contact with lesion of untreated patient is possible but rare |
| RT and GIT: 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 present |
| RT and GIT: Standard Precautions. | |
| Aerosolized powder, environmental exposures: Respirator (N95 mask or powered air-purifying respirator), protective clothing; decontamination of persons with powder on them (see http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5135a3.htm) | |
| Hand hygiene: Handwashing for 30 to 60 seconds with soap and water or 2% chlorhexidene gluconate after spore contact; alcohol hand rubs are inactive against spores.981 | |
| Postexposure prophylaxis after environmental exposure: A 60-day course of antimicrobials (doxycycline, ciprofloxacin, or levofloxacin) and postexposure vaccine under IND. |
| Disease | Botulism |
|---|---|
| Site(s) of infection; transmission mode | GIT: Ingestion of toxin-containing food; RT: Inhalation of toxin containing aerosol. Comment: Toxin ingested or potentially delivered by aerosol in bioterrorist incidents. LD50 for type A is 0.001 μg/mL/kg. |
| Incubation period | 1 to 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. |
| Disease | Ebola Hemorrhagic Fever |
|---|---|
| Site(s) of infection; transmission mode | As a rule, infection develops after exposure of mucous membranes or RT, or through broken skin or percutaneous injury. |
| Incubation period | 2 to 19 days, usually 5 to 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% of patients. |
| Diagnosis | Etiologic diagnosis can be made using reverse-transcription-PCR, serologic detection of antibody and antigen, pathologic assessment with immunohistochemistry, and viral culture with electromicroscopic confirmation of morphology, |
| Infectivity | Person-to-person transmission occurs primarily through unprotected contact with blood and body fluids; percutaneous injuries (eg, needlestick) are associated with a high rate of transmission. Transmission in health care settings has been reported but can be 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, then the 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, then Droplet Precautions can be substituted for Airborne Precautions. Emphasize the following: (1) use of sharps safety devices and safe work practices, (2) proper hand hygiene, (3) barrier protection against blood and body fluids on 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 and Contact Precautions) and segregate patients from those not suspected as having VHF infection. Limit blood draws to those essential to care. See the text for discussion and Appendix A for recommendations for naturally occurring VHFs. |
| Disease | Plague∗ |
|---|---|
| Site(s) of infection; transmission mode | RT: Inhalation of respiratory droplets. Comment: Pneumonic plague is most likely when used as a biological weapon, but some cases of bubonic and primary septicemia also may occur. Infective dose, 100 to 500 bacteria. |
| Incubation period | 1 to 6 days, usually 2 to 3 days. |
| Clinical features | Pneumonic: Fever, chills, headache, cough, dyspnea, rapid progression of weakness, and, in later stages, hemoptysis, circulatory collapse, and bleeding diathesis. |
| Diagnosis | Presumptive is diagnosis from Gram's stain or Wayson's stain of sputum, blood, or lymph node aspirate; definitive diagnosis is from cultures of same material or paired acute/convalescent serology. |
| Infectivity | Person-to-person transmission occurs through respiratory droplets. Risk of transmission is low during the first 20 to 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 and Droplet Precautions until patients have received 48 hours of appropriate therapy. Chemoprophylaxis: Consider antibiotic prophylaxis for HCWs with close contact exposure. |
| Disease | Smallpox |
|---|---|
| Site(s) of infection; transmission mode | RT 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) likely will result. | |
| Incubation period | 7 to 19 days (mean, 12 days). |
| Clinical features | Fever, malaise, backache, headache, and often vomiting for 2 to 3 days, followed by 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 a World Health Organization–approved laboratory (CDC); detection by PCR available only at select LRN laboratories, the CDC, and US Army Medical Research Institute of Infectious Diseases. |
| Infectivity | Secondary attack rates up to 50% in unvaccinated persons. Infected persons may transmit disease from the time that rash appears until all lesions have crusted over (about 3 weeks). Infectivity is greatest during the first 10 days of rash. |
| Recommended precautions | Combined use of Standard, Contact, and Airborne Precautions should be maintained until all scabs have separated (3 to 4 weeks).† Only immune HCWs should care for patients. Postexposure vaccine should be provided within 4 days. |
| Vaccinia‡: HCWs to cover vaccination site with gauze and semipermeable dressing until scab separates (≥ 21 days). Hand hygiene should be observed. | |
| Adverse events with virus-containing lesions: Standard Precautions plus Contact Precautions until all lesions are crusted. |
| Disease | Tularemia |
|---|---|
| Site(s) of infection; transmission mode | RT: Inhalation of aerosolized bacteria; GIT: 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 to 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 PCR (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 |
AIIR, airborne infection isolation room; BSL, biosafety level; CSF, cerebrospinal fluid; CT, computed tomography; CXR, chest x-ray; ELISA, enzyme-linked immunosorbent assay; GIT, gastrointestinal tract; HCW, health care worker; IHC, immunohistochemistry; LD50, lethal dose for 50% of experimental animals; LRN, Laboratory Response Network; PAPR, powered air-purifying respirator; PCR, polymerase chain reaction; RT, respiratory tract; VHF, viral hemorrhagic fever.
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 to 24 hours) apparently pose little risk (Wu L-T. A treatise on pneumonic plague. Geneva, Switzerland: League of Nations; 1926; Kool JL. Risk of person-to-person transmission of pneumonic plague. Clin Infect Dis 2005;40:1166-72). 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 (Butler TC. Plague and other Yersinia infections. In: Greenough WB, editor. Current topics in infectious disease. New York: Plenum; 1983). 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 occurs only after close contact. Simple protective measures, such as wearing masks, maintaining good hygiene, and avoiding close contact, have been effective in interrupting transmission during many pneumonic plague outbreaks; in the United States, the last known case of person-to-person transmission of pneumonic plague occurred in 1925 (Kool JL. Risk of person-to-person transmission of pneumonic plague. Clin Infect Dis 2005;40:1166-72).
Transmission by the airborne route is a rare event. Airborne Precautions are recommended when possible, but in the event of mass exposures, Barrier Precautions and containment within a designated area are most important.204, 212
Vaccinia adverse events with lesions containing infectious virus include inadvertent autoinoculation, ocular lesions (blepharitis, conjunctivitis), generalized vaccinia, progressive vaccinia, and eczema vaccinatum. Bacterial superinfection also requires addition of Contact Precautions if exudates cannot be contained.216, 217