Smallpox

Background

• Caused by the variola virus
• Passed through direct contact with the person, with body fluids, as well as with airborne droplets of an infected, symptomatic person
• Most infectious during the first week of symptoms, but will remain infectious until the last pox scab falls off
• Humans are the only known host
• Declared eradicated in 1980 after a global immunization campaign from 1966-1980; last known natural case was in Somalia in 1977; last known cases were in England in 1978 after a laboratory accident

Bioterrorism

• There are stocks of the virus in 2 laboratories – one in Atlanta, Georgia, USA and one in Moscow, Russia
• There are concerns some laboratories may illegally have the virus and could release it as a weapon of bioterrorism
  • This was attempted by British soldiers in 1763 by throwing blankets from people with smallpox to the American Indians
• In July 2014, 2 vials of smallpox were unknowingly discovered at the National Institutes of Health in Bethesda, Maryland leading to heightened concerns that there may be more stockpiles in the world
• Many proposals have been made to destroy all the remaining vials of smallpox and related viruses, but as of yet the virus remains in those 2 laboratories

Vaccination History

• The vaccine “vaccinia variola” was made from a closely-related virus
• Discovered by Edward Jenner who found out that the milkmaids who had been exposed to cowpox were immune to smallpox
• Vaccination is considered successful if at least one pustule forms at the injection site
• Does have serious side effects, especially in the immunocompromised, including death in rare cases
• Due to the side effects and the current eradication, it is not used anywhere in the world currently
• Many governments have large stockpiles of the vaccinia vaccine and plans in place for rapid response and vaccination if an outbreak were to occur

Clinical Features

• Incubation period: 7-19 days
• Initial phase begins as a fever, fatigue/weakness, dorsal-lumbar pain, myalgias, nausea/vomiting
• 2-4 days later the characteristic rash appears
  • Worst on the face, arms, legs, and includes the palms and soles
  • Lesions will generally all be at same stage
  • Lesions begin as clear fluid-filled vesicles, progress to pustules, and then harden and form a crust, ultimately falling off in about 3-4 weeks
• Several different disease courses
  • Variola minor – most common form of the disease, described above
  • Variola fulminans – rapid death during the initial phase
  • Variola confluens – initial maculopapular rash becomes confluent leading to 96% mortality
  • Variola hemorrhagica – hemorrhages occur within the blisters as well as mucus membranes and internal organs, death usually occurs during the first 24 hours

Child with Smallpox

Workup

• Clinical diagnosis based on symptoms and characteristic rash
• PCR DNA test
• When the disease was present, either electron microscopy of stained crusts of lesions or a slide precipitation method was used

Differential Diagnosis

Pediatric Rash

• Atopic dermatitis
• Bed bugs
• Contact dermatitis
• Drug rash
• Erythema infectiosum (Fifth disease)
• Hand-foot-and-mouth disease
• Henoch-schonlein purpura (HSP)
• Herpangina
• Herpes simplex virus (HSV)
• Infectious mononucleosis
• Meningitis
• Measles
• Molluscum contagiosum
• Roseola infantum
• Rubella (German measles)
• Scabies
• Scarlet fever
• Smallpox
• Varicella (Chickenpox)

Treatment

• IMMEDIATE NOTIFICATION OF PUBLIC HEALTH AUTHORITIES
• Vaccine administered up to 3 days post-exposure was effective in preventing infection as well as lessening the severity of the disease if infection occurred

Post-Exposure Prophylaxis

• Vaccinia Vaccine (administer within 72hrs of exposure)

Active Disease

• Supportive care and wound care for open lesions
• Vaccinia Vaccine within the first 72hrs can decrease total disease severity and within 7 days may decrease symptoms
  • Vaccination is not efficacious once the patient has developed rash

Vaccinia Vaccine Complications

Contraindications for administration include:

• Pregnancy
• Severe cardiac disease
• Immunocompromise
• Same living quarters as other person with above contraindications
  • due to viral shedding

Isolation

• Airborne and contact isolation with negative pressure
• Personal protective wear level D with N95 respirator

See Also

Bioterrorism

References

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