Infectious Disease Book

http://www.fpnotebook.com/

SmallpoxAka: Small Pox, Variola, Vaccinia, Poxvirus, Orthopoxvirus, Cowpox

Advertisement

  1. See Also
    1. Smallpox Vaccine
  2. Epidemiology
    1. No natural source of Smallpox remains
    2. Biological Weapon potential
    3. Outbreaks historically occurred in winter
      1. Same time as Varicella Zoster Virus and Measles
  3. History
    1. British first used Smallpox as Biological Weapon
      1. French and Indian Wars 1754-1767
      2. Distributed contaminated blankets to Native Americans
    2. Edward Jenner demonstrated efficacy of vaccine 1796
      1. Found milkmaids who had cowpox did not get Smallpox
      2. Initiated Cowpox inoculation which prevented Smallpox
    3. Eradication of Smallpox completed in 1977
      1. Smallpox Vaccination discontinued
        1. United States: 1972
        2. Worldwide: 1980
      2. Most labs destroyed variola virus samples by 1999
  4. Pathophysiology
    1. Brick-shaped 200 nm member of Orthopoxvirus genus
    2. Cowpox also member of Orthopoxviruses
  5. Types
    1. Standard Smallpox (90% of cases)
      1. Variola Major (much more severe form)
      2. Variola Minor
    2. Severe variants
      1. Hemorrhagic Smallpox (more common in pregnant women)
      2. Malignant Smallpox
  6. Transmission
    1. Contagious only after onset of rash
      1. Infectious for first 7 to 10 days after rash
      2. Infectivity wanes after scabs form
      3. Only very low dose (few virions) needed for infection
    2. Direct contact with oropharyngeal droplets or aerosols
    3. Contaminated clothing or linen
    4. No animal or insect hosts
  7. Symptoms
    1. Incubation period of 7 to 17 days (usually 12-14 days)
    2. Viral prodrome
      1. High fever
      2. Malaise
      3. Headache
      4. Backache
      5. Abdominal Pain
  8. Signs: Rash
    1. Location
      1. Initial: Oropharynx, face and forearms
      2. Later: Spreads to trunk and legs
    2. Typical Smallpox Characteristics
      1. Initial: Maculopapular
      2. Next: Vesicles or Oral Ulcers within 1-2 days
      3. Next: Round, tense and embedded Pustules
      4. Next: Crusts or scabs form by 8-9 days of rash
      5. Last: Scars form with Sebaceous Gland destruction
    3. Hemorrhagic Smallpox Characteristics
      1. Initial: Dusky erythema
      2. Next: Petechiae
      3. Next: Hemorrhaging from skin and mucus membranes
    4. Malignant Smallpox Characteristics
      1. Initial: Slow confluence of lesions
      2. Next: Soft, flattened, velvety Vesicles form
      3. Next: Reddish fine-grained skin coloration
      4. Contrasts: No formation of Pustules or scabs
  9. Differential Diagnosis
    1. Varicella Zoster Virus (features of VZV listed)
      1. No lesions on palms or soles in VZV
      2. VZV with minimal prodrome; fever onset with rash
      3. Stages of maturation much faster in VZV
        1. Rash develops rapidly
        2. Scab forms within 7 days of rash
        3. Scab separates within 14 days of rash
      4. Trunk more involved in VZV than face or extremities
    2. Meningococcemia
      1. Contrast with Hemorrhagic or Malignant Smallpox
    3. Severe Acute Leukemia
      1. Contrast with Hemorrhagic or Malignant Smallpox
  10. Labs (used to identify epidemic)
    1. Obtain samples from possible source
      1. Open Vesicle with scalpel and dab with cotton swab
      2. Obtain scab sample with forceps
    2. Send sample in sealed Vacutainer (tape top)
    3. Encase Vacutainer in second, water proof container
    4. Send samples to high-containment labs (BL-4)
    5. Smallpox rapidly identified under electron microscopy
  11. Management: Emergently reduce transmission risk
    1. Patient Isolation at facility (home is preferred)
      1. Negative pressure room
      2. High-efficiency particulate air filtration
      3. Deceased patients should be cremated
        1. Vaccinate mortuary workers
    2. Protect all medical facility personnel
      1. Medical care by recently vaccinated persons only
      2. Immunize all hospital employees
      3. Furlough non-immunized employees
      4. Infectious precautions (Gloves and Mask)
      5. Contact public health immediately
      6. Decontamination
        1. Laundry in biohazard bags, autoclave, then launder
        2. Waste in biohazard bags and incinerate
        3. Room Decontamination per protocol
    3. Identify and immunize contacts of infection source
      1. Household or face-to-face contact with febrile source
      2. Isolate if fever >101 within 17 days of exposure
      3. Forced quarantine may be necessary
  12. Management: Medical
    1. See Prevention below (include postexposure prophylaxis)
    2. Symptomatic care
    3. Cidofovir (Vistide) is currently being researched
  13. Prognosis
    1. Variola Major: 30% mortality rate
    2. Variola Minor: 1-2% mortality rate
    3. Hemorrhagic Smallpox: Uniformly fatal by day 6 of rash
    4. Malignant Smallpox: Frequently fatal
  14. Prevention
    1. Pre-exposure Smallpox Vaccination
      1. Immunity wanes after 5-10 years
      2. Those vaccinated 30 years ago are likely susceptible
    2. Post-exposure Prophylaxis
      1. Vaccinia Immune Globulin 0.6 ml/kg IM
        1. Must be given within 3 days (ideal within 24 hours)
      2. Smallpox Vaccination
        1. Must be given within 4 days of exposure
    3. Variola Immunoglobulin
      1. High risk patients
      2. Consider if Immunization contraindicated
    4. Cidofovir
      1. May be efficacious if used within 2 days of exposure
  15. References
    1. Wilson (1991) Harrison's IM, McGraw-Hill, p. 709-11
    2. Breman (1998) N Engl J Med 339:556
    3. Henderson (1999) JAMA 281:2127

Cowpox (C0010232)

Definition (MSH)A mild, eruptive skin disease of milk cows caused by COWPOX VIRUS, with lesions occurring principally on the udder and teats. Human infection may occur while milking an infected animal.
ConceptsDisease or Syndrome (T047)
ICD9051.0
MSHD015605
EnglishCow Pox, Cowpox, yaba
Spanishviruela vacuna
Parent ConceptsCowpox and paravaccinia (C0153016), Poxviridae Infections (C0032870), Disease due to Orthopoxvirus (C1532229)
SourcesCSP, DXP, ICD9CM, MSH, MTH, NDFRT, SCTSPA, SNOMEDCT
Derived from the NIH UMLS (Unified Medical Language System)


Poxviridae (C0032868)

Definition (CSP)family of dsDNA viruses; replication occurs in the cytoplasm with inclusion bodies; natural host range is narrow; transmission is by several routes including airborne, fomites, direct contact and mechanically by arthropods.
Definition (MSH)A family of double-stranded DNA viruses infecting mammals (including humans), birds and insects. There are two subfamilies: CHORDOPOXVIRINAE, poxviruses of vertebrates, and ENTOMOPOXVIRINAE, poxviruses of insects.
Definition (NCI)A family of double-stranded DNA viruses infecting mammals, birds and insects. Contains two subfamilies: chordopoxvirinae, poxviruses of vertebrates, and entopoxvirinae, poxviruses of insects.
ConceptsVirus (T005)
MSHD011212
EnglishFamily Poxviridae, pox virus, Poxviridae, Poxvirus, Poxvirus group, Poxviruses
Spanishfamilia Poxviridae, grupo Poxvirus
Parent ConceptsDNA Viruses (C0012923), Poxviridae (C0032868), dsDNA viruses, no RNA stage (C1005544), Double Stranded DNA Virus (C1512048), Outdated concept (C1274014)
SourcesAOD, CSP, MSH, MTH, NCBI, NCI, SCTSPA, SNOMEDCT
Derived from the NIH UMLS (Unified Medical Language System)


Smallpox (C0037354)

Definition (MSH)An acute, highly contagious, often fatal infectious disease caused by an orthopoxvirus characterized by a biphasic febrile course and distinctive progressive skin eruptions. Vaccination has succeeded in eradicating smallpox worldwide. (Dorland, 28th ed)
ConceptsDisease or Syndrome (T047)
ICD9050, 050.9
MSHD012899
EnglishClassical smallpox, Ordinary smallpox, Smallpox, Variola, Variolas
Spanishvariola, viruela, viruela clasica
Parent ConceptsSmallpox (C0037354), Viral diseases with exanthemata NOS (C0153062), Poxviridae Infections (C0032870), Virus Diseases (C0042769), Exanthema (C0015230), Skin Diseases, Viral (C0162628), Disease due to Orthopoxvirus (C1532229)
SourcesCSP, DXP, ICD9CM, LCH, MEDLINEPLUS, MSH, MTH, NCI, NDFRT, SCTSPA, SNOMEDCT
Derived from the NIH UMLS (Unified Medical Language System)


Vaccinia (C0042214)

Definition (MSH)The cutaneous and occasional systemic reactions associated with vaccination using smallpox (variola) vaccine.
ConceptsDisease or Syndrome (T047)
MSHD014615
EnglishVaccinia, Vaccinias
Spanishvaccina, vaccinia, variola vaccina
Parent ConceptsPoxviridae Infections (C0032870), Pox virus infection of skin (C0406050), Disease due to Orthopoxvirus (C1532229)
SourcesDXP, LCH, MSH, MTH, NDFRT, SCTSPA, SNOMEDCT
Derived from the NIH UMLS (Unified Medical Language System)


Orthopoxvirus (C0206580)

Definition (MSH)A genus of the family POXVIRIDAE, subfamily CHORDOPOXVIRINAE, comprising many species infecting mammals. Viruses of this genus cause generalized infections and a rash in some hosts. The type species is VACCINIA VIRUS.
ConceptsVirus (T005)
MSHD018155
EnglishGenus Orthopoxvirus, Orthopoxvirus, Orthopoxviruses, Vaccinia subgroup, Vaccinia subgroup virus
Spanishgenero Orthopoxvirus, ortopoxvirus, subgrupo del virus de la vaccinia, subgrupo del virus vacunal
Parent ConceptsChordopoxvirinae (C0206570)
SourcesCSP, LNC, MSH, NCBI, SCTSPA, SNOMEDCT
Derived from the NIH UMLS (Unified Medical Language System)



Navigation Tree