Smallpox was a highly contagious disease caused by the variola virus, which historically killed about 30% of its victims and left many survivors with severe scarring or blindness. For centuries, this illness was a devastating plague, causing an estimated 300 million deaths in the 20th century alone. Smallpox remains the only human infectious disease ever to be globally eradicated.
Smallpox Status and Current Medical Responses
The virus no longer circulates outside of secure laboratories. If an accidental or intentional release were to occur today, medical science has prepared a multi-pronged response focused on treatment and containment. The most immediate and effective intervention is vaccination, which acts as a post-exposure prophylactic (PEP). If the smallpox vaccine is administered within three to four days of exposure, it can prevent the disease or significantly lessen the severity of the symptoms.
Beyond the vaccine, modern medicine has developed specific antiviral drugs that did not exist during the eradication campaign. The U.S. Food and Drug Administration (FDA) has approved two primary antiviral agents for smallpox: tecovirimat (TPOXX) and brincidofovir (Tembexa). Tecovirimat works by blocking a protein necessary for the virus to spread from cell to cell, while brincidofovir inhibits viral DNA synthesis. These medications are available through government stockpiles for use in a confirmed outbreak.
The Global Campaign to Eliminate the Virus
A cure for smallpox ultimately became unnecessary because of a determined global health effort to eliminate the virus entirely. The World Health Organization (WHO) launched the Intensified Smallpox Eradication Programme in 1967. They recognized that the disease only infected humans and had no animal reservoir, making eradication a realistic goal. This campaign moved away from relying solely on mass vaccination, which proved difficult in remote areas, and instead adopted a strategy of surveillance and containment.
The cornerstone of this new strategy was “ring vaccination,” a highly targeted method. Once a case of smallpox was identified, public health teams would quickly isolate the patient and then vaccinate everyone who had been in close contact with that individual. This created a protective “ring” of immunity. This approach efficiently focused limited resources and stopped the chain of transmission at its source.
The success of this focused effort was momentous. The last naturally occurring case of the variola minor strain was reported in Somalia in October 1977. Two and a half years later, in May 1980, the World Health Assembly officially declared the global eradication of smallpox. This achievement marked the end of a disease that had afflicted humanity for thousands of years.
Why Smallpox Remains a Global Health Concern
Despite the eradication success, the variola virus still exists, which is the reason it remains a global health concern. The virus is officially held in secure, controlled laboratory stockpiles at two World Health Organization collaborating centers. These are the U.S. Centers for Disease Control and Prevention (CDC) in Atlanta and the State Research Centre of Virology and Biotechnology (VECTOR) in Russia. These stocks are retained for research, such as developing new vaccines and antiviral drugs, but their existence is the subject of ongoing debate.
The two main risks associated with these remaining viral stocks are accidental release and intentional misuse. An unintentional release, though highly unlikely given the high-security containment, presents a threat because the virus is highly contagious. The second concern is the potential for the virus to be used as a bioweapon. Variola is classified as a Category A biological weapon due to its ease of dissemination and high fatality rate.
The risk is amplified because routine smallpox vaccination ceased in the general population decades ago following eradication. This means the vast majority of the global population under the age of 40 has no immunity, making them highly susceptible to the disease. Public health authorities must therefore maintain preparedness, ensuring the availability of effective countermeasures and surveillance systems.