A LEAN FIGURE cast in bronze kneels beside a child, a tiny lancet in his hand poised to strike at the girl’s left shoulder. Another patient waits her turn, upper arm revealed. The memorial, outside the World Health Organization headquarters in Geneva, celebrates the global conquest of smallpox in 1980, a milestone that belongs on any list of reasons to be cheerful: Variola major gorged on our species for thousands of years, blazing a trail of hideous pustules that disfigured victims’ bodies and faces and wiped out communities. Children and the elderly were especially vulnerable, and those not felled by the disease were sometimes blinded by it.

The Geneva memorial honours the physician as warrior in the eradication of smallpox. On a Pfizer campus in Pennsylvania, a twin statue tells a different story, positioning Big Pharma as the hero. Neither monument, however, recalls the many casualties of smallpox, and this says a great deal about what we choose to remember.

One of the last major outbreaks in Canada began in the spring of 1862 when a ship from San Francisco arrived in Victoria and patient zero stepped ashore. Throughout the summer and autumn, smallpox raced north and east, up the coast and inland through canyons of tightly packed settlements that were perfectly suited to its appetite....