Smallpox advisories and resources for King County health care providers |
Report all suspected cases of smallpox immediately to Public Health - Seattle & King County by calling 206-296-4774.
- 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.
Microbiology and pathogenesis |
- 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.
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