Smallpox natural history: Difference between revisions
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===Pustular rash=== | ===Pustular rash=== | ||
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* Bumps turn into [[pustules]] | * Bumps turn into [[pustules]] | ||
Revision as of 18:23, 10 July 2014
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
Overview
Natural History
Smallpox, considered to be eradicated since 1980 by the WHO, caused death throughout the world. Affecting mainly children, young adults and family members of the infected patients, symptoms depended on the form of the disease present. For the most common form, the ordinary smallpox, the symptoms usually evolved according to the following sequence:
Incubation period
- Usually 12 - 14 days
- Asymptomatic
Prodrome period
- Usually 2 - 4 days
- Fever
- Malaise
- Muscle pain and headache
- Vomiting
Early rash
- About 4 days
- Most contagious stage
- Rash as small red spots in the mouth
- Rash turns into sores releasing the virus
- Rash appears on the skin, starting on the face, moving towards arms and hands, eventually spreading to the rest of the body within 24 hours
- At this time, fever usually falls and the person feels better
- At the 3rd day of rash, it turns into raised bumps
- At the 4th day of rash, bumps are filled with fluid, with a central depression
- Fever will then raise again, until scabs are formed
Pustular rash
- About 5 days
- Contagious
- Bumps turn into pustules
Pustules and scabs
- About 5 days
Resolving scabs
- About 6 days
Resolved scabs
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 prognosis of smallpox depends on the form of the disease:
Variola major
Ordinary smallpox
- Fatality rate about 10% for patients with discrete lesions and 60% for those with confluent lesions[1]
- In fatal cases, death usually occurs between the 10th and 16th days of the illness
- Unclear cause of death, however infection was known to involve multiple organs
- Possible contributors include:
- Circulating immune complexes
- Severe viremia
- Uncontrolled immune response
Flat-type smallpox
- Fatality rate about 90%
- Cause of death commonly included: loss of fluids, electrolytes and protein, as well as severe sepsis
Hemorrhagic-type smallpox
- Fatality rate near 100%, usually between 6th and 7th day after the beginning of fever
- Cause of death was often heart failure, or in late cases intense viremia, with severe platelet loss and weak immune response
Variola minor
- Fatality rate about ≤1%
References
- ↑ Moore, Zack S; Seward, Jane F; Lane, J Michael (2006). "Smallpox". The Lancet. 367 (9508): 425–435. doi:10.1016/S0140-6736(06)68143-9. ISSN 0140-6736.