Current Incidence of Smallpox
The current incidence of smallpox is zero—the disease has been completely eradicated from nature since 1977, with the World Health Organization certifying global eradication in 1980. 1
Historical Context and Eradication
- The last naturally occurring case of smallpox was documented in Somalia in 1977, followed by one laboratory-acquired infection in the UK in 1978. 1, 2, 3
- In May 1980, the World Health Assembly officially certified that the world was free of naturally occurring smallpox after approximately 2.5 years of surveillance following the last natural case. 1, 3
- Smallpox is estimated to have caused 300-500 million deaths worldwide during the 20th century before its eradication. 2
Current Status and Biosecurity Concerns
While naturally occurring smallpox no longer exists, the variola virus remains stored in only two authorized high-security laboratories: the CDC in Atlanta, USA, and the Vector Center in Koltsovo, Russia. 2
Theoretical Risk Considerations
- The risk of smallpox occurring as a result of deliberate release by terrorists exists but is considered low, with no identifiable at-risk population. 1
- Because routine vaccination ceased in the United States in 1971 for civilians and 1990 for military personnel, the global population is now highly susceptible to smallpox infection. 1, 2, 4
- The virus's high transmissibility and historical 30% mortality rate make it a significant biothreat agent despite eradication. 1, 4, 5
Public Health Preparedness
Current vaccination recommendations are limited to specific high-risk groups rather than the general population:
- Laboratory workers who directly handle orthopoxviruses (vaccinia, monkeypox, cowpox, variola) or recombinant vaccinia viruses. 1
- Designated smallpox response teams at federal, state, and local levels prepared to investigate and respond to any suspected cases. 1
- Healthcare workers who would provide direct care for suspected or confirmed smallpox cases in the event of an outbreak. 1
Surveillance Infrastructure
- Any febrile rash illness for which smallpox is considered in the differential diagnosis must be immediately reported to local or state health departments. 1
- Laboratory confirmation is available only at CDC, with preliminary diagnosis possible within 8-24 hours. 1
- The National Pharmaceutical Stockpile maintains protocols for rapid delivery of smallpox vaccine to every state and U.S. territory within 12-24 hours if needed. 1
Clinical Significance
The practical implication for clinicians is that smallpox should remain on the differential diagnosis for severe febrile rash illnesses only in the context of suspected bioterrorism or laboratory exposure. 1 The disease does not occur naturally, so any confirmed case would represent either an intentional release or laboratory accident requiring immediate public health notification and response. 1