Flying the Yellow Jack: Microbes in Defense of America

Examinations of war and its winners, from a twentieth-century perspective, tend to privilege personalities and technologies. Great civilizations march, the latest weapons in hand, behind great generals—or competent bureaucrats.

For twentieth-century conflicts, this emphasis may in fact carry significant explanatory power, but the historical liability of living in a post-twentieth-century world resides in how atypical the last century was relative to all that came before. One striking difference, as J. R. McNeill points out in Mosquito Empires, is the paramount role of the disease microbes with which we as humans have coevolved. The biological and cultural magnitude of sickness is difficult to overstate in the era before the establishment of germ theory, antibiotics, inoculations, and public health campaigns. Disease was a horror that stalked families, cities, nations, and armies, all of whom had mournfully inadequate means to fight what they could not see and did not understand. Westerners, whose Christian tradition was founded in part on stories of a man who could heal the sick, looked to saints and pseudoscience for aid. Even into the early twentieth century, patent medicines were among the most commonly advertised items in the pages of popular periodicals.

We have begun to appreciate the biological and strategic place of disease in warfare. Before the early twentieth century, we can chalk up more casualties to the invasion and rapid reproduction of microbes than to the bravery and weapons of troops. Although it took centuries to fully uncover, Alfred Crosby's Ecological Imperialism: The Biological Expansion of Europe, 900-1900 (1986) demonstrated the asymmetrical role of virgin-soil epidemics, which eliminated some 90 percent of America's indigenous peoples and an even higher percentage in the Caribbean basin. Philip Curtin's Disease and Empire: The Health of European Troops in the Conquest of Africa (1998) displays the defensive role that disease played in slowing European imperialism and impeding settlement in tropical Africa. And we have begun, in works such as Andrew McIlwaine Bell's Mosquito Soldiers: Malaria, Yellow Fever, and the Course of the American Civil War (2010) to examine more carefully the role of disease in specific conflicts.

McNeill, however, in a book impressive for its sweep and originality, demonstrates that there is still much we do not understand about the militant role of microbes in our past conflicts. Rather than scrutinize a specific war or battle, Mosquito Empires tests its central argument over a period of nearly three centuries in a large, coherent ecological region, the Greater Caribbean (p. 2). McNeill argues that microscopic species, specifically the yellow fever virus and malarial protozoa, shaped America's broadest political contours on a scale similar to that of the previous hemispheric conquest. From Africa, yellow fever arrived in force by the middle of the seventeenth century, decimating peoples of non-African descent, especially in port cities. But within a few short generations, yellow fever's status switched from epidemic to endemic among much of the region's population. Like chicken pox today, it became a disease of non-immune children who generally suffered infection without symptoms and acquired life-long immunity. And this development—what McNeill refers to as a regional "differential immunity"—lies at the heart of his thesis: for the next 250 years, invading Europeans tried to settle, capture, or hold on to territories in the greater Caribbean, but nearly every attempt failed because the new disease regime of yellow fever, and to a lesser extent malaria, worked to the full advantage of homegrown armies over invaders. In case after case—cases almost to excess—McNeill narrates the assaults, the mortalities, and the consequences for American geopolitics. Whether they were attempts to settle little contested spaces (the Scots at Darien or the French at Guyana), repeated attempts to capture prize Spanish ports (Cartagena and Havana), or later attempts to maintain control over colonies that threatened to break away (British North America, Saint Domingue, New...