smallpox

Scientists cleaning out an old laboratory on the National Institutes of Health campus in Bethesda, Md., last week came across a startling discovery: vials labeled "variola" — in other words, smallpox.

Under international convention, there are supposed to be only two stashes of this deadly virus: one at the federal Centers for Disease Control and Prevention in Atlanta, and another at a similar facility in Russia.

The CDC swooped in to collect the vials and carted them off to a secure lab at its Atlanta headquarters.