Smallpox is an acute infectious virus which devastated many populations historically. With concerns about bioterrorism rising in the late 20th century, some people have wondered if smallpox still exists. The short answer to this is yes; the long answer is a bit more complicated.

In 1967, the World Health Organization (WHO) announced a global campaign to eliminate smallpox through vaccination. Numerous WHO employees traveled the globe, seeking out cases of naturally occurring smallpox and vaccinating the surrounding population to prevent its spread. In 1979, the WHO announced that the last wild case of smallpox had been documented, effectively vanquishing the disease. However, several laboratories retained samples of the disease, used in research and vaccine development.

Scientists argued that the samples of live virus in labs shouldn't be destroyed, as they might some day be needed for research. If, for example, someone managed to engineer smallpox, perhaps from vaccine scabs collected prior to 1979, it would pose a serious bioterrorism threat. In addition, a natural pox virus might potentially evolve into a fatal illness, in which case samples of smallpox for comparison might be very useful when developing a vaccine.

As a result, it was agreed that two laboratories would retain samples, one in the United States and one in Russia. The American stock of the vaccine is located at the Centers for Disease Control (CDC) headquarters in Atlanta, Georgia, where it is tightly guarded and periodically checked for integrity. The Russian stock is kept in Siberia, at the Vector State Research Center for Virology and Biotech, and these samples are also supposed to be closely guarded, although some international organizations have raised questions about the security at Vector.

Some scientists are also concerned that other countries may actually have samples of the virus, or that they may have access to vaccine scabs, which carry a small reservoir of DNA which could be sequenced. Some of these samples may also have come from Vector, which has struggled with security issues. In the 1990s, this led to increased global concern about bioterrorism, since a large portion of the population had not been vaccinated for smallpox. It has also been suggested that the vaccine may not last for a lifetime, so a huge portion of the world could be vulnerable to the release of wild smallpox.

For this reason, several countries have checked their vaccine stockpiles, to ensure that they are still good. In addition, several companies keep samples of part of the virus for use in making vaccines, ensuring that smallpox could be quickly dealt with if it emerges again.