An outbreak of smallpox was the furthest thing from historian Dr. Paul Levengood's mind when his staff at the Virginia Historical Society put together an exhibit of "bizarre bits" that were added to the society's collection since its founding in 1831, The Wall Street Journal reported Thursday.

There was Confederate president Jefferson Davis's cigar, confiscated by Union troops. There was a fungus carving of Robert E. Lee on his horse, Traveller, and a wreath made of human hair.

Then someone mentioned a letter, handwritten and dated 1876, with what appeared to be a smallpox scab pinned inside -- light brown, about the size of a pencil eraser and crumbling.

The scab got the attention of the Centers for Disease Control and Prevention (CDC), home to one of the world's two known caches of live smallpox viruses....