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

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 4 days post-exposure was effective in preventing infection as well as lessening the severity of the disease if infection occurred
• Symptomatic treatment
• No cure
• Newer antiviral medications created since the eradication of smallpox could be an effective treatment but have never been tested on smallpox as the disease is no longer present in humans

Complications

• Disfigurement / scarring
• Blindness if the corneas were involved
• Death

Prevention

• 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

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

See Also

Bioterrorism

Sources

• Barquet, Nicolau, MD, and Pere Domingo, MD. "Smallpox: The Triumph over the Most Terrible of the Ministers of Death." Annals of Internal Medicine 127 (1997): 635-42.
• Ellner, P. D. "Smallpox: Gone but Not Forgotten." Infection 26.5 (1998): 263-69.
• Langefeld, TW, J. Engel, T. Menges, and G. Hempelmann. "Smallpox - Clinic, Therapy and Anesthetic Aspects (part 1)." Anasthesiol Intensivmed Notfallmed Schmerzther 38.7 (2003): 445-55.
• Rosen, Peter, John A. Marx, Robert S. Hockberger, and Ron M. Walls. "Smallpox." Rosen's Emergency Medicine Concepts and Clinical Practice. 8th ed. Vol. 2. Philadelphia, PA: Elsevier/Saunders, 2013. 1579-1580.
• "Smallpox, Smallpox FAQ." WHO | World Health Organization. http://www.who.int/csr/disease/smallpox/en/ & http://www.who.int/csr/disease/smallpox/faq/en/

<<http://www.ncbi.nlm.nih.gov/pubmed/23011963>> <<http://www.ncbi.nlm.nih.gov/pubmed/18406986>> <<http://www.ncbi.nlm.nih.gov/pubmed/16168312>>