Smallpox natural history: Difference between revisions

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{{Smallpox}}
{{Smallpox}}
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{{CMG}}; {{AE}} {{JS}}


==Overview==
==Overview==
The [[natural history]] and [[outcome]] of [[smallpox]] depend on the form of disease. The common progress will start with [[flu]]-like [[symptoms]] followed by a [[skin rash]] that generally progresses in a typical fashion, leading to the formation of scabs that will fall off, leaving a scar. The [[complications]] may include [[respiratory]] conditions, from [[bronchitis]] to [[pneumonia]], but may also involve the [[joints]], [[bones]] and/or [[eyes]]. The overall [[fatality rate]] for the ''variola major'' form was about 30%.


==Natural History==
==Natural History==
[[Smallpox]], considered eradicated since 1980 by the [[WHO]], affected mainly children, young adults and family members of [[infected]] patients. [[Symptoms]] depended on the form of the disease. For the most common form, the ''ordinary smallpox'', [[symptoms]] usually developed according to the following sequence:<ref name=CDC>{{cite web | title = Smallpox disease overview | url = http://www.bt.cdc.gov/agent/smallpox/overview/disease-facts.asp }}</ref>
===Incubation period===
* Duration approximately 12 - 14 days
* Noncontagious
* [[Asymptomatic]]
===Prodrome period===
* Duration approximately 2 - 4 days
* Sometimes [[contagious]]
* [[Fever]]
* [[Malaise]]
* [[Muscle pain]] and [[headache]]
* [[Vomiting]]
===Early rash ===
* Duration approximately 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===
* Duration approximately 5 days
* [[Contagious]]
* Bumps turn into [[pustules]]
===Pustules and scabs===
* Duration approximately 5 days
* [[Contagious]]
* [[Pustules]] first form a crust and than a scab
===Resolving scabs===
* Duration approximately 6 days
* Scabs start to fall leaving scars not the [[skin]]
* [[Contagious]], until all scabs have fallen
* Most scabs will have fallen 3 weeks after start of [[rash]]
===Resolved scabs===
* All scabs have fallen off
* Person is no longer [[contagious]]


==Complications==
==Complications==
Common complications of smallpox include:
Common [[complications]] of [[smallpox]] include:
* Respiratory complications (viral or bacterial):
* [[Respiratory]] [[complications]] ([[viral]] or [[bacterial]]):
:* [[Bronchitis]]
:* [[Bronchitis]]
:* Fatal [[pneumonia]]
:* Fatal [[pneumonia]]
* Secondary [[bacterial]] skin infection
* Secondary [[bacterial]] [[skin infection]]
* [[Encephalitis]] - 1 in 500 patients, commonly in adults
* [[Encephalitis]] - 1 in 500 patients, commonly in adults
* Permanent pitted [[scars]]
* Permanent pitted [[scars]]
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:* [[Corneal ulcer]]
:* [[Corneal ulcer]]
:* [[Iritis]]
:* [[Iritis]]
:* Iridocylcitis
:* [[Iridocylcitis]]
:* 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.  
:* [[Conjunctiva|Subconjunctival]] and [[retinal]] [[hemorrhages]].  
* [[Osteomyelitis]] - lesions are symmetrical, most common in the [[elbows]], [[tibia]], and [[fibula]]
* [[Osteomyelitis]] - lesions are symmetrical, most common in the [[elbows]], [[tibia]], and [[fibula]]
* [[Arthritis]] may lead to [[limb]] deformities
* [[Arthritis]] may lead to [[limb]] deformities
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==Prognosis==
==Prognosis==
The prognosis of smallpox depends on the form of the disease:
The [[prognosis]] of [[smallpox]] depends on the form of the disease:


===Variola major===
===Variola major===
====Ordinary smallpox====
====Ordinary smallpox====
* Fatality rate about 30%
* [[Fatality rate]] about 10% for patients with discrete lesions and 60% for those with confluent lesions<ref name="MooreSeward2006">{{cite journal|last1=Moore|first1=Zack S|last2=Seward|first2=Jane F|last3=Lane|first3=J Michael|title=Smallpox|journal=The Lancet|volume=367|issue=9508|year=2006|pages=425–435|issn=01406736|doi=10.1016/S0140-6736(06)68143-9}}</ref>
* In fatal cases, death usually occurs between the tenth and sixteenth days of the illness
* In fatal cases, death usually occurs between the 10th and 16th days of illness
* Unclear cause of death, however infection was known to involve multiple organs.
* Unclear cause of death
* Infection often affected multiple [[organs]]
* Possible contributors include:
* Possible contributors include:
:* Circulating [[immune complexes]]
:* Circulating [[immune complexes]]
:* Severe [[viremia]]
:* Severe [[viremia]]
:* Uncontrolled [[immune response]]
:* Uncontrolled [[immune response]]


====Flat-type smallpox====
====Flat-type smallpox====
* Fatality rate about 90%
* [[Fatality rate]] about 90%
* Cause of death commonly included: loss of fluids, electrolytes and protein, as well as severe sepsis
* Cause of death commonly included: loss of fluids, [[electrolytes]] and [[protein]], as well as severe [[sepsis]]


====Hemorrhagic-type smallpox====
====Hemorrhagic-type smallpox====
* Fatality rate near 100%, usually between 6th and 7th day after the beginning of fever
* [[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
* Cause of death was often [[heart failure]], or in late cases intense [[viremia]], with severe [[platelet]] loss and weak [[immune response]]


===Variola minor===
===Variola minor===
* Fatality rate about ≤1%
* [[Fatality rate]] about ≤1%


==References==
==References==
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[[Category:Needs overview]]
[[Category:Needs overview]]
[[Category:Disease]]
[[Category:Disease]]
[[Category:Infectious disease]]
 
[[Category:Pediatrics]]
[[Category:Pediatrics]]
[[Category:Smallpox]]
[[Category:Smallpox]]

Latest revision as of 19:04, 18 September 2017

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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

The natural history and outcome of smallpox depend on the form of disease. The common progress will start with flu-like symptoms followed by a skin rash that generally progresses in a typical fashion, leading to the formation of scabs that will fall off, leaving a scar. The complications may include respiratory conditions, from bronchitis to pneumonia, but may also involve the joints, bones and/or eyes. The overall fatality rate for the variola major form was about 30%.

Natural History

Smallpox, considered eradicated since 1980 by the WHO, affected mainly children, young adults and family members of infected patients. Symptoms depended on the form of the disease. For the most common form, the ordinary smallpox, symptoms usually developed according to the following sequence:[1]

Incubation period

  • Duration approximately 12 - 14 days
  • Noncontagious
  • Asymptomatic

Prodrome period

Early rash

  • Duration approximately 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

Pustules and scabs

Resolving scabs

  • Duration approximately 6 days
  • Scabs start to fall leaving scars not the skin
  • Contagious, until all scabs have fallen
  • Most scabs will have fallen 3 weeks after start of rash

Resolved scabs

  • All scabs have fallen off
  • Person is no longer contagious

Complications

Common complications of smallpox include:

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[2]
  • In fatal cases, death usually occurs between the 10th and 16th days of illness
  • Unclear cause of death
  • Infection often affected multiple organs
  • Possible contributors include:

Flat-type smallpox

Hemorrhagic-type smallpox

Variola minor

References

  1. "Smallpox disease overview".
  2. 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.

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