Several secure laboratories around the world have maintained small stores of the smallpox virus, known as variola, for use in biomedical research, and for vaccine production in case the disease -- eradicated decades ago as a public health threat -- were ever to make a reappearance.  The U-S Centers for Disease Control and Prevention is one of the few places in the world where samples of the smallpox virus are still stored. 

Researcher Joseph Esposito led a team there that created genetic maps of the DNA sequences in their samples.  One aim was to get a better picture of the virus' genetic diversity.

"We took a cross section, which amounts to about 45 different clinical samples of the virus," Esposito explains, "and we did the DNA sequencing on these different ones and what that told us is that these viruses don't have a great deal of genome variation."  Esposito says he had suspected the samples would be similar, "because the same vaccine was able to eradicate the disease from the world.  And these isolates represent a very tiny sample of the virus samples that were collected from about the end of World War II from the mid-1940s to the end of the smallpox eradication program in the 1970s."

Esposito says knowing the gene sequence could help scientists design an antiviral drug that would be effective against all the strains of smallpox in the world.  He notes that the former Soviet Union reportedly ran a bio-warfare lab that may have used smallpox to create weapons.  The American researcher believes knowing the smallpox gene sequence will permit scientists to scale up vaccine production quickly in response to bio-terrorism.