Background
• Characterized by low visibility, high potency, accessibility, easy delivery
• Only small amount of agent needed to kill large numbers of people
• Only plague, smallpox, & viral hemorrhagic fevers spread from person to person
Approach
• Take protective measures: Universal precautions w/ HEPA filter masks, decontaminate pt including remove clothing, shower w/ soap & water
• Isolation (negative pressure room) of affected, proper disposal of corpses
ANTHRAX (BACILLUS ANTHRACIS)
History
• Contact w/ infected goats, sheep, cattle, horses, swine, 1–6 d incubation period
• Most commonly cutaneous infection, also respiratory or GI; not human to human
• Fever, malaise, HA, cough, weakness, SOB, pruritus, N/V, diarrhea, abd pain
• Less likely than influenza to have sore throat or rhinorrhea
Findings
• Dependent on route of inoculation
• Cutaneous (95%): Incubation 1–12 d; starts as small papule → vesicle containing serosanguineous fluid (1–2 d) → vesicle rupture leaves painless necrotic lesion w/ surrounding edema → massive edema
• Ulcer base develops 1–5 cm black eschar; after 2–3 wks separates & leaves scar
• Inhalational: Incubation 1–6 d; initial nonspecific sxs & cough × 2–3 d → sudden onset respiratory distress (dyspnea, stridor, cyanosis, ↑ CP, diaphoresis) → rapid onset shock & death in 24–36 h
• GI: From ingestion of infected meat; incubation 2–5 d; local oral/tonsillar ulcer, dysphagia & respiratory distress → abdominal pain, hematemesis, massive ascites, diarrhea
Evaluation
• Blood cultures; Gram stain or culture confirms cutaneous anthrax, serologies, rapid antianthrax antibody test can be performed w/i 1 h
• Difficult to diagnose inhalational or GI anthrax
• CXR (inhalational): Mediastinal widening, pl effusion
Treatment
• Early abx: PCN, doxycycline, ciprofloxacin IV. Multiple abx if systemic/extensive dz.
• Raxibacumab injection recently FDA approved for inhalational anthrax
• Prophylaxis: Ciprofloxacin or doxycycline PO; anthrax vaccine
• Corticosteroids may be useful in severe edema, meningitis
Disposition
• Consider admission based on clinical findings
Pearls
• Large, aerobic, gram-positive, spore-forming, nonmotile, pyogenic B. anthracis
• Found in animals in South & Central America, Southern & Eastern Europe, Africa, Asia, Caribbean, Middle East
• Death from respiratory failure, overwhelming bacteremia, septic shock, meningitis
• Mortality variable: Cutaneous <1%, inhalational 45–92%, GI 25–60%
PLAGUE (YERSINIA PESTIS)
History
• Contact w/ rat flea; 99% cases in SE Asia (Vietnam), rarely Southwest United States
• Acute onset high fevers, LAD, myalgias, cough, SOB, CP, hemoptysis, sore throat, GI sx
Findings
• Bacilli spread to lymph nodes → supportive lymphadenitis, producing bubo → spread to other organs (spleen, liver, lungs, skin) & septic shock if untreated
• Bubonic (85–90%): Incubation 1–8 d; buboes emerge in groin, axilla, or cervical regions w/ f/C/HA, N/V, AMS, cough → buboes visible in 24 h, severely painful
• Septicemia (10–15%): Result of hematogenous dissemination of bubonic plague
• Pneumonic (1%): From inhalation of aerosols or hematogenous dissemination; productive cough w/ blood-tinged sputum, rales, decreased breath sounds
Evaluation
• Presence of painful bubo; Gram stain of bubo aspirate; blood, sputum, & CSF cultures, lymph node aspiration
• CXR (pneumonic): Bilateral alveolar infiltrates, consolidation
Treatment
• Isolate pts for 1st 48 h after tx; if pneumonic plague, isolate for 4 d
• Levofloxacin recently approved
• Streptomycin 15 mg/kg IM BID × 10 d ± doxycycline 200 mg IV × 1
• Alternative regimens: Chloramphenicol, gentamicin, Bactrim, ciprofloxacin
• Septicemia plague: Same as for other causes of sepsis
• Prophylaxis: Doxycyclin or ciprofloxacin PO × 7 d; use insecticides, reduce rodent populations
Disposition
• Admission, isolation
Pearls
• Y. pestis: Gram-negative nonmotile nonsporulating coccobacillus; can remain viable for days → weeks in water, moist soil, grain, buried bodies; reservoir: Rodents
• Mortality variable: Untreated bubonic 50%, Septic/pneumonic ∼100%; tx reduced mortality to 10–15% overall
SMALLPOX (VARIOLA)
History
• High fever, HA rigors, malaise, myalgias, vomiting, abdominal pain, back pain, rash
Findings
• Virus multiplies in respiratory tract
• Incubation 12 d, spreads hematogenously → regional lymph nodes, blood vessels → skin changes
• 2 types: Major (30% mortality), minor (<1% mortality)
• 2–3 d after initial sxs, exanthema on face, hands, forearms → trunk & lower extremities
• Skin exanthem: Macules → papules (day 2) → vesicles (day 5) → umbilicated pustules (day 8); pustules form scabs after 8–14 d; death in 2nd week from toxemia
Evaluation
• Clinical Dx; centrifugal distribution, lesions all in same stage of development, PCR
Treatment
• Isolation, hemodynamic support, skin care, vaccination w/i 4 d of exposure
Disposition
• Isolation × 17 d; pts most infectious on day 3–6 after onset of fever, remain infectious until all scabs separated
Pearls
• Variola virus: Highly infectious by aerosol, environmentally stable, prolonged infectivity
• Transmitted through respiratory droplets, bodily fluids
• Last occurrence in Somalia in 1977; routine vaccination stopped in 1972