Smallpox

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smallpox (variola)

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-DNA virus member of genus orthopox virus
-large, complex virus
-brick shaped
-highly stable
-retains infectivity for long periods outside the host
-infectious dose 10-100 organisms

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variola major

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-severe and most common form of smallpox with mortality rate of 30%

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variola minor

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-milder form of disease with sparse rash and ~1% mortality rate

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transmission of smallpox

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1. direct face to face contact (infected aerosols and air droplets)
2. direct contact with infected bodily fluids and contaminated objects
3. incubation period ~12 days
4. pts not contagious in incubation period
5. pt most contagious with onset of rash. Less contagious at prodrome
6. not spread by insects and animals
7. humans are only natural hosts

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clinical manifestations

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-asx viremia on 3rd - 4th day
-virus multiplies in spleen, bone marrow, LNs
-secondary viremia on 8th day followed by fever and toxemia
-virus localizes in smal blood vessels of dermis and oral mucosa
-infects adjacent cells
-at end of 12-14 days, sudden onset of fever, HA, backache, vomiting, delerium. Lasts 2-4 days
-fleeting rash
-in 2-3 days spots in mouth become spores

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rash of smallpox

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-begins as pink macules on face, arms, legs
-by 3rd day, macules enlarge and become raised papules which become tense blisters, vesicle ~6mm in diameter deep in the skin
-~day 6, fluid in blister becomes turbid and then becomes pus-filled with depression in center
-by days 11-14 of illness, pus filled lesions shrink and dry up and form crusts in skin

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rash cont

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-days 15-21 scabs separate leaving a scar
-dried material contains smallpox virus
-pt contagious until all scabs have fallen off
-extent of rash correlates wth severity of illness
-in severe cases rash covers entire body

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where is the rash

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-most dense on face and extremities
-lesions develop and evolve at the same rate
-other than skin and mucosa, other organs not involved

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diagnosis of smallpox

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-clinical ssx
-isolation of virus from bl or lesions ,electron microscopy, cx, PCR, DNA probes
-state and local health dept labs should be immediately contacted

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tx of smallpox

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-no antivirals have been proven effective
-cidofovir being studied
-supportive: IV fluids, pain control, antipyretics
-abx for secondary bacterial infxs
-vaccination within 4 days of exposure may offer protection against acquiring infx

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postexposure isolation and infx control

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-pt should be isolated
-Contacts should receive vaccine and carefully monitored to see if in incubation period. Isolation for 17 days after contact. Temps monitored. If > 101F infection suggested. Maintain isolation until dx made

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vaccinations for high risk groups

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-In case of outbreak, high risk groups given priority to receive vaccination
-Persons exposed to virus
-other workers (laundry, medical waste, mortuary)
-law enforcement, emergency response, military personnel
-Contacts of smallpox patients
-Personnel involved in care or transport of patients
-Lab workers collecting or processing specimens
-anyone in hospital with someone with smallpox

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smallpox vaccination

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-most effective given within 3 days of exposure
-does not confer lifelong immunity
-vaccinia virus vaccine (Dryvax) contains live vaccinia virus but not variola virus
-Following inoculation, vaccine produces an immune reaction that protects against smallpox

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C/I to vaccine

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1. eczema or contact dermatitis
2. immunosuppression
3. pregnancy/breastfeeding
4. allergy to vaccine

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vaccine administration

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-2 prolonged needle with droplet of vaccine
-given over deltoid without prep skin
-needle perpendicular to skin
-3 strokes of needle in 5 mm area. 15 strokes for revaccination.
-trace of blood ensures proper vaccination
- no dressing

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complications of vaccination

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-local rxns:
1. sore arm
2. edema
3. inflammation
4. swelling
5.intense erythema
-systemic rxns: fever, malaise, myalgia
-inadvertent inoculation of other sites or other peopel

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complications of vaccination: Progressive vaccinia

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-necrosis of area of vaccination
-hospitalize and tx with VIG
-most common in IC pts
-75% fatality rate

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complications: generalized vaccinia

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-vesicles or pustules on nml skin distant from vaccination site from viremia

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complications: eczema vaccinatum

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-virus implants in skin disrupted by eczema or atopic dermatitis
-tx: hospitalization and vaccinia immune globulin (VIG)

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vaccinia immune globulin intravenous (VIGIV)

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-human plasma derived product to treat some complications of smallpox vaccination.
-Made from pooled plasma of donors who received Dryvax
-VIGIV used to treat vaccine complications such as severe skin infections