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

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	Epidemiology
	Microbiology
	Clinical presentation
	Diagnosis
	Infection control
	Medical management
	Prophylaxis
	Web resources

• Smallpox was declared eradicated from the world in 1980.
• Two smallpox virus strains exist: Historically, variola major had a case fatality rate of approximately 30% and variola minor, of less than 1%.
• Smallpox is transmitted person-to-person primarily through close contact (i.e., within 6.5 feet) by respiratory droplets; it may also be transmitted through aerosols and direct contact.

Smallpox and Bioterrorism

• Smallpox is of high concern for use as a biological weapon because of its potential high morbidity, lack of a treatment (other than supportive), and low immunity status of the current population.

• The causative agent is variola, a double-stranded DNA virus in the genus, Orthopoxvirus.
• The virus enters the body via the oropharynx or respiratory mucosa, spreads systemically, and eventually localizes in small blood vessels of the dermis.

Smallpox "Syndromes"

• Ordinary type (90% of cases)
• Modified type (a milder form; occurs in 25% of previously immunized & 2% of non-immunized)
• Variole sine eruptione (febrile illness in previously vaccinated)
• Flat type (7% of cases; case fatality 97%)
• Hemorrhagic type (<3% of cases; case fatality 96-100%)

Ordinary smallpox

• The incubation period is 12 to 14 days (range, seven to 17 days).
• Initial prodrome is two to four days in duration: High fever (>101º F), prostration, headache, backache, chills, vomiting, and severe abdominal pain.
• The characteristic exanthem begins on the face, hands, and forearms and spreads to the lower extremities and trunk.
• Lesions progress in stages of one to two days duration each: macules to papules to vesicles to pustules to scabs.
• Lesions are in the same stage of development at one time on any one area of the body and are more prevalent on the face, proximal extremities, palms, and soles.
• Exanthem may be preceded by an enanthem on the oropharyngeal mucosa.
• Patients are infectious from the onset of rash until all scabs separate (14 to 21 days).

• Specimen collection for laboratory diagnosis should be conducted by trained staff using strict infection control precautions.
• Laboratory diagnosis is conducted by public health laboratories and CDC.
  • WA State Public Health Lab: Direct fluorescent antibody (DFA) for varicella zoster (VZV) and herpes simplex virus (HSV), VZV serologies, PCR for enterovirus, vaccinia, orthopoxviruses and variola virus
  • CDC: electron microscopy, variola PCR, orthopoxvirus culture, serology
• Contact hospital infection control and Public Health - Seattle & King County (PHSKC) immediately for suspected cases of smallpox.

• Airborne and contact precautions should be followed by all health care providers, staff, and visitors (i.e., gown, gloves, N95 mask).
• Only vaccinated individuals (within the past three years, or those without contraindications to vaccination) should provide care to suspected smallpox patients.
• Respiratory and contact isolation is required for all hospitalized patients.
  • Private, negative pressure room with HEPA-filtered exhaust.

Management is supportive; there is no specific treatment.

• Monitoring and treating complications:
  • Hemorrhage/DIC
  • Secondary bacterial infections
  • Corneal ulceration and/or keratitis
  • Arthritis or "Osteomyelitis variolosa."
  • Bronchitis, pneumonitis, pneumonia, or pulmonary edema
  • Encephalitis
  • Other: nausea, vomiting, diarrhea, orchitis
• Monitoring and maintaining fluid and electrolyte balance.
• Skin care: Allow scabs to separate and heal naturally; do not apply salves or ointments.

• Smallpox vaccine (Dryvax^® Vaccinia Vaccine)
• Made from live Vaccinia virus (not Variola).
• Reconstituted in a diluent containing 50% glycerin, and a trace of phenol; also contains polymyxin B, streptomycin, tetracycline, and neomycin.
• Administered by intradermal inoculation with a bifurcated needle (“scarification”).
• Vaccination site is monitored for evidence of a “major take,” six to eight days post-vaccination.
• Protection after primary vaccination exists for three to five years, and probably is present at lower levels for 10 to 15 years post-vaccination.
• Cross-protection occurs for other Orthopoxviruses.
• Vaccination within four days of exposure to smallpox will prevent or significantly modify the severity of disease.
• In the event of known smallpox exposure, the risk of disease outweighs the potential risks from vaccination.
• Contraindications for vaccination in the absence of current known cases of smallpox include:
  • a history of atopic dermatitis (or eczema),
  • active acute, chronic, or exfoliative skin conditions that disrupt the epidermis,
  • pregnancy,
  • an immunocompromised state,
  • known cardiac disease or three or more risk factors for cardiac disease,
  • close contacts of individuals with any of the above conditions, and
  • allergy to any vaccine component.
• Vaccine adverse events:
  • Fever, transient maculopapular rash, and inadvertent autoinoculation are the most common vaccine-related adverse events.
  • For additional information on vaccine adverse events and their management, please see the CDC smallpox vaccine Web site: www.bt.cdc.gov/agent/smallpox/vaccination/clinicians.asp.
  • Vaccinia immune globulin (VIG) and possibly Cidofovir (investigational) may be used to treat some serious adverse reactions to vaccine.
• New vaccines are under investigation.

• Centers for Disease Control and Prevention Smallpox Response Plan and Guidelines
  
  
• Evaluating Patients for Smallpox - Acute, Generalized Vesicular and Pustular Rash Illness Protocol (PDF)
  
  
• Smallpox vaccination
  
  
• Infectious Disease Society of America
  
  
• Bioterrorism training modules
  
  
• Washington State Department of Health