I'd say the thing I liked best about the Wall Street Journal article this post is based on is that it satisfactorily explained why people were keeping the scabs at all. [Brief aside: newspapers, I recently learned, at times adopted their names by the way they received the news they printed. So the Nashua Telegraph got its news via telegraph while the Charleston Post and Courier got its news via the mail and by rider. Neat, huh?] At any rate, the Journal article concerns the recent arrival of CDC officials at the Virginia Historical Society's exhibit "Bizarre Bits," and the removal of an item on display, a smallpox scab that was discovered in the Society's archives pinned to a letter sent from a man to his father in 1876.
The CDC, which made news recently after releasing suggestions for preparing for a zombie apocalypse, learned of the old-timey scab when a Virginia electrical engineer who read a write-up of the exhibit and started a phone tree of concern that branched from his neighbor to the National Institutes of Health and ultimately to the CDC right here in beautiful Atlanta, GA, one of only two cities in the world where a legal store of live smallpox can be found. The other is in Russia, and recently the World Health Organization has been entertaining pleas that the stores be destroyed once and for all.
Smallpox is the only disease considered officially eradicated, a success announced in 1980. The dread disease had a terrible effect o Europe and Asia during the late Middle Ages onward; in Europe, an estimated 400,000 people died each year from the disease while in the New World following contact, an initial mortality rate of about 90 percent among Amerindians is the current mortality estimate. Worldwide the mortality figures reach between 300 and 500 million deaths in the 20th century alone. And this was the century that the disease was eradicated, remember -- a full 20 years before its close.
Although smallpox is considered eradicated, the scab in the Virginia Historical Society's collection shows that there are likely other samples of the disease still extant and unaccounted for. The WSJ article mentions that immunologists have been known to find old vials of the virus in their freezers and that cemeteries are likely lousy with the deadly virus. That there are any of us left after the disease swept across the continents of the world shows that we can develop immunity to the disease. Indeed, Islamic physician and medical scholar Rhazes noted the acquired immunity granted to anyone who survived communication of the disease as far back as 910 A.D. Smallpox is considered eradicated because we managed to create a vaccine that introduced a less virulent form of the disease to the human body, allowing it to mount a defense against any successive, more virulent versions of the disease.
And it is here that we reach the reason people in the late-19th century would pin smallpox scabs to letters addressed to people they called "Pa": It was an easy method of immunization. The scab in the Virginia Historical Society was taken from the arm of an infant that had been vaccinated against smallpox. Bits of scabs were introduced into cuts in the skin as a means of immunization. The letter writer notes that there is enough in the scab to vaccinate 12 people.
He also makes mention of a previous scab shipment that "Pa" lost. More unaccounted stores of the disease unaccounted for. [youtube=http://www.youtube.com/watch?v=1iXfZ1eYdtA&w=610]