Pox_ An American History - Michael Willrich [25]
The slow accumulation of epidemiological experience would eventually persuade public health officials that mild type smallpox was a distinct disease entity. In 1913, Charles V. Chapin of the Providence Health Department, one of the preeminent American health officials of the early twentieth century, published the first major scientific article on the history of mild type smallpox in the United States. Basing his article on the evidence from public health reports, Chapin suggested that the mild type “seems to be a true mutation” with a marked tendency to “breed true.” That is, mild type smallpox begot more of the same. Mild smallpox could still give rise, in susceptible individuals, to horrifying confluent smallpox; it could even kill. Infants, the elderly, and people with preexisting health problems were especially vulnerable. But, said Chapin, “tho it is possible that a few outbreaks of the severe type may have developed from the mild type, there is no conclusive evidence that they have been numerous, or extensive.” Twenty years later, Chapin stated his claim in stronger terms. Citing the belief of “practically all epidemiologists and health officers who have had experience with smallpox in the United States,” he wrote, “there is no proof that, during the more than thirty years the mild type has been with us, it has ever given rise to a permanent strain of the severe type.” That remains the consensus of smallpox scientists today.8
Experts now believe that two strains of mild smallpox appeared for the first time at the tail end of the nineteenth century. One probably arose in the southeastern part of North America (the Pensacola strain), the other a bit earlier in southern Africa. Laboratory studies would eventually show that the two regional varieties of smallpox had different DNA, but their clinical and epidemiological characteristics were so similar that scientists created one term to cover both: variola minor. Classical smallpox was given a new name: variola major. Until the advent of genetic testing, the only sure way to tell variola minor from variola major was to count bodies. Variola minor was defined in the scientific community as that form of the virus that killed between 0.1 percent and 2 percent of its victims.9
Since the 1910s, the North American strain of variola minor has been referred to by its Brazilian name, alastrim, a Portuguese word that means “burns like tinder, scatters, spreads from place to place.” The name encapsulates its global history. Since many of its victims remained ambulatory, and because so much of the U.S. population at the turn of the century moved around the country in pursuit of work and profit, alastrim spread with unusual speed over great distances. From its likely southern origin, it traversed the United States from 1896 to 1902, slipped into Latin America, England, and Europe, then made its way around the world. In other words, the disease so many Americans called “Cuban itch” was almost certainly a U.S. export.10
Variola major did not go away. The classical form of the virus apparently caused those deadly epidemics in New Orleans, New York, Boston, and elsewhere in 1900 and afterward. The virus in its deadliest form continued to infect and kill millions of people around the globe until the 1970s. In the United States, however, the incidence of variola major declined sharply after 1905. (The last major epidemic struck Ohio, Michigan, and western Pennsylvania in 1924–25.) After the turn-of-the-century epidemics, then, the mild type became the only form of smallpox most American communities would ever know.11
Government officials must often act in tight situations with imperfect knowledge. It’s part of the job description. Health officials in the late nineteenth-century South