Quick Facts about Smallpox
Information adapted from the CDC and Johns Hopkins Center for Civilian Biodefense Center.
Signs and symptoms
Post-exposure prophylaxis
Treatment
Signs and symptoms
- Smallpox is caused by the variola virus
- Incubation period is about 12 days (7 to 17 days)
- Mode of transmission
-
- Person to person by infected saliva droplets
- May be spread by contaminated clothing or bedding
- Most infectious during first week
- Remain infectious until scabs fall off
- Initial symptoms
-
- Fever, fatigue, head and back aches
-
- The absence of significant fever prodrome makes smallpox very unlikely.
- 50% vomiting, 10% diarrhea
- Characteristic rash within 2 -3 days
-
- Begins on face, proximal arms and legs
- Spreads to chest, distal extremities
-
- Most concentrated on the face and distal extremities
- At any one time, the rash is in the same stage of development on any one part of the body
- Stages of rash
- Flat, red rash followed in 2 days by
- Papules followed in 4 -5 days by
- Vesicles followed in 1 - 2 days by
- Pustules followed in 7 - 14 days by
- Crusts and scabs followed by
- Scabs falling off and scarring (2 - 3 weeks)
- Disease in previously vaccinated persons
-
- Vaccination ended in 1972
- Current level of immunity is unknown
- Persons are assumed to be susceptible
- Complications
-
- Secondary bacterial infections of the skin
- Keratitis and corneal ulceration
- Viral arthritis and osteomyelitis
- Bacterial pneumonia
- Orchitis
- Encephalitis
- Differential diagnosis
-
- Varicella (chickenpox)
-
- Rash begins on trunk, spreads to face and extremities
- Most lesions are concentrated on trunk or equally distributed between trunk and extremities
- At any one point in time, rash in different stages
- Diagnostic Tests
-
- Clinical presentation
- Virus culture
-
- Skin lesions, oropharynx, conjunctiva, urine
- Serological testing for antibody
-
- Pared samples 2 - 3 weeks apart
- Hemagluttination inhibition, compliment fixation, or gel precipitation
- DFA and IFA can be used to diagnose varicella-zoster virus
- Case fatality rate 30%
Post-exposure Prophylaxis
- The vaccine lessens severity or prevents illness
- Must be given within 4 days after exposure
- Vaccine
-
- Live vaccina virus
- Does not contain smallpox virus
Treatment
- No antiviral treatment available
- Antibiotics for secondary bacterial infections
- Supportive care (fluids, pain, fever)
- Mass vaccination for the general public is not recommended
-
- Risk currently outweighs benefits
- Sufficient vaccine not available
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