Smallpox natural history: Difference between revisions
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:* Optic [[atrophy]] | :* Optic [[atrophy]] | ||
:* [[Blindness]] - occurs in 35% to 40% of eyes affected with keratitis and corneal ulcer | :* [[Blindness]] - occurs in 35% to 40% of eyes affected with keratitis and corneal ulcer | ||
:* Subconjunctival and [[retinal]] hemorrhages. | |||
* [[Osteomyelitis]] - lesions are symmetrical, most common in the [[elbows]], [[tibia]], and [[fibula]] | |||
* [[Arthritis]] may lead to [[limb]] deformities | |||
* [[Ankylosis]] | |||
==Prognosis== | ==Prognosis== | ||
Revision as of 17:07, 10 July 2014
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Smallpox Microchapters |
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Smallpox natural history On the Web |
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Risk calculators and risk factors for Smallpox natural history |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Natural History
Complications
Common complications of smallpox include:
- Respiratory complications (viral or bacterial):
- Bronchitis
- Fatal pneumonia
- Secondary bacterial skin infection
- Encephalitis - 1 in 500 patients, commonly in adults
- Permanent pitted scars
- Eye problems - 2% of all cases; pustules can form on the eyelid, conjunctiva, and cornea, leading to:
- Conjunctivitis
- Keratitis
- Corneal ulcer
- Iritis
- Iridocylcitis
- Optic atrophy
- Blindness - occurs in 35% to 40% of eyes affected with keratitis and corneal ulcer
- Subconjunctival and retinal hemorrhages.
- Osteomyelitis - lesions are symmetrical, most common in the elbows, tibia, and fibula
- Arthritis may lead to limb deformities
- Ankylosis
Prognosis
The overall case-fatality rate for ordinary-type smallpox is about 30%, but varies by pock distribution: ordinary type-confluent is fatal about 50–75% of the time, ordinary-type semi-confluent about 25–50% of the time, in cases where the rash is discrete the case-fatality rate is less than 10%. The overall fatality rate for children younger than 1 year of age is 40%–50%. Hemorrhagic and flat types have the highest fatality rates. The fatality rate for flat-type is 90% or greater and nearly 100% is observed in cases of hemorrhagic smallpox. The case-fatality rate for variola minor is 1% or less. There is no evidence of chronic or recurrent infection with variola virus.
In fatal cases of ordinary smallpox, death usually occurs between the tenth and sixteenth days of the illness. The cause of death from smallpox is not clear, but the infection is now known to involve multiple organs. Circulating immune complexes, overwhelming viremia, or an uncontrolled immune response may be contributing factors. In early hemorrhagic smallpox, death occurs suddenly about six days after the fever develops. Cause of death in hemorrhagic cases involved heart failure, sometimes accompanied by pulmonary edema. In late hemorrhagic cases, high and sustained viremia, severe platelet loss and poor immune response were often cited as causes of death. In flat smallpox modes of death are similar to those in burns, with loss of fluid, protein and electrolytes beyond the capacity of the body to replace or acquire, and fulminating sepsis.