Why Is the Smallpox Virus Still Kept in Laboratories?

Smallpox is the only human disease eradicated worldwide, but scientists still keep live samples of the virus frozen in government laboratories in the United States and Russia. The decision has remained controversial for more than four decades.

The disease ranks among the deadliest infections in human history. It is estimated to have killed about 300 million people during the 20th century alone. Although vaccination eliminated smallpox globally, the frozen samples are considered alive because they could become infectious if properly thawed.

Institutions such as the U.S. Centers for Disease Control and Prevention and the United Kingdom Health Security Agency preserve live samples of various pathogens to support the development of vaccines, treatments and diagnostic tools. Some experts argue that smallpox virus remains scientifically valuable because researchers can use it to study viral evolution and its interaction with the immune system.

Others say scientists already have enough information to continue research without live virus, including the virus’s complete genomic sequence. Supporters of destruction also point to a World Health Organization review commissioned in 2010, which concluded that the remaining stocks had no essential role in protecting public health.

The case for retaining the samples also reflects concern that unknown stocks may exist elsewhere. In 2014, workers found six forgotten vials of freeze-dried smallpox virus dating from the 1950s in a laboratory in Maryland. Since people are no longer routinely vaccinated against smallpox, an accidental outbreak could be catastrophic. The WHO has repeatedly delayed previously planned destruction dates, leaving the debate unresolved.