Journal of Interdisciplinary History, XLIX:3 (Winter, 2019), 397–417. Benjamin Reilly Cardinal Numbers: Changing Patterns of Malaria and Mortality in Rome, 494–1850 For the past two millennia, Rome has probably attracted more foreign visitors from Europe than any other European city. As the seat of an ancient empire, and the theoretical capital of the revived Holy Roman Empire founded by Charlemagne in 800, Rome was for centuries highly coveted by German monarchs seeking the imperial crown, not to mention territory, influence, and revenue south of the Alps. Pilgrims came to Rome in a steady stream from at least the eighth century; after 1300, these streams swelled into rivers during the years of the holy Jubilees. Moreover, as the mother city of the mother church, Rome attracted a parade of litigants, job-seekers, envoys, and diplomats from every corner of Europe, as well as newly elected bishops and archbishops who were encouraged, or required, to have their offices validated by the pope. Rome was also a city of the arts, not just because of the still-standing ves- tiges of antiquity but also because of the Church’s patronage of resident colonies of painters, artists, and scholars, who attracted “Grand Tourists” from the seventeenth to nineteenth centuries. Many roads, and many motives, carried Europeans to Rome.1 Unfortunately, these roads led to a destination rendered dan- gerous by endemic malarial fevers. Rome lies within the northern Benjamin Reilly is Associate Teaching Professor of History, Carnegie Mellon University, Qatar. He is the author of Slavery, Agriculture, and Malaria in the Arabian Peninsula (Athens, 2015); Man and Disaster: Case Studies in Nature, Society, and Catastrophe ( Jefferson, N.C., 2009); Tropical Surge: Ambition and Disaster on the Edge of America, 1831–1935 (Sarasota, 2005). © 2018 by the Massachusetts Institute of Technology and The Journal of Interdisciplinary History, Inc., https://doi.org/10.1162/jinh_a_01302 1 For a typical example of Rome’s attraction for northern Europeans, see Lassels, who declared in 1670 that Rome was “the head, and the Mistresse of the world, and Earthly Goddesse; the Eternal City, The Compiendum of the World; the Common Mother ....[InRome,] all lan- guages are spoken, all sciences are taught, the ablest men of Europe meet, all the best records are found, all wits appear as upon their true theatre, all foreign Ambassadors render themselves, all Nuncios at their return to Rome unload themselves of the observations they have made abroad; and where every stone almost is a book; every statue a master; every inscription a lesson, every Antechamber an Academy” (Richard Lassels, The Voyage of Italy, Or a Compleat Journey through Italy [London, 1670], 5, 257). Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/jinh_a_01302 by guest on 25 September 2021 398 | BENJAMIN REILLY range of A. labranchiae, a variety of Anopheles mosquitoes that, unlike its northern cousins (such as A. atroparvus), is highly anthropo- philic, preferring blood meals from humans more than from animals. This preference makes A. labranchiae a highly effective vector for ma- laria parasites. What is more, Rome and its environs lie within the 15°C isotherm line, and thus hosts high enough annual temperatures to sup- port P. falciparum malaria, a far deadlier species than the P. vivax and P. malariae parasites found elsewhere in northern Europe (see Figure 1). Demographical factors, especially chronic underpopulation, contributed to Rome’s malaria problems as well. After reaching a peak of more than one million inhabitants during the imperial era, Rome’s population had plummeted to 100,000 by the fifth century and then to only 25,000 by the high Middle Ages, leaving large tracts of land within the ancient city walls abandoned to farming or to pasturage. This underpopulation aggravated Rome’s malaria prob- lem. Unlike respiratory and diarrheal diseases, which usually decline as population density decreases, malaria infections can rise even while population drops. Abandoned lands around the periphery of the shrinking city can provide mosquitoes with staging grounds from which to penetrate the urban core.2 Basic geographical factors also conspired to make Rome and its vicinity highly malarial. Although Rome’sfamoussevenhills were protected from infection to some extent, given mosquitoes’ difficulties in flying uphill, much of Rome’s territory is marshy and/or within the floodplain of the Tiber River and thus an excel- lent habitat for mosquitoes. As Ziegler pointed out, Rome’s uneven geography left the city interspersed with low-lying drainage zones, each of which was a hot spot of disease within the city proper. Human alterations to the landscape further aggravated this problem; “ditches and ruts . cisterns, troughs, waste ground and ruined buildings” all served as “ideal breeding grounds” for Rome’smosquito 2 “Anopheles labranchiae—Factsheet for Experts,” European Centre for Disease Prevention and Control, available at https://ecdc.europa.eu/en/disease-vectors/facts/mosquito-factsheets/ anopheles-labranchia (accessed August 31, 2017). See also Michelle Ziegler, “Malaria Landscapes in Late Antique Rome and the Tiber Valley,” Landscapes, XVII (2016), 141. In 1155, a visitor to Rome described the “disabitato”—the mostly uninhabited area within Rome’swalls—as “mostly wasteland, set with ruins, where green snakes, black toads and winged dragons hid, whose breath poisoned the air.” As late as the nineteenth century, the disabitato was still regarded with suspicion, associated with “swamps and stagnating ponds” from which arose “dark mists laden with fever” (Richard Krautheimer, Rome: Profile of a City, 312–1308 [Princeton, 2000], 317). Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/jinh_a_01302 by guest on 25 September 2021 MALARIA AND MORTALITY IN ROME | 399 Fig. 1 Mosquitoes and Average Temperatures in Italy vectors. Due in part to deforestation of the surrounding highlands, the Tiber carried a heavy silt load, which “create[d] marshes at any obstruction or constricted point, and frequently change[d] its course.” As a result, most of the land in the Tiber River valley and the surrounding plains of the Agro Romano had a reputation for seasonal fevers, which resulted in sparse settlement from late anti- quity up until at least the mid-nineteenth century. Despite its poten- tial agricultural fertility, this zone was exploited primarily through transhumant pastoralism as well as cereal cultivation, using labor sea- sonally recruited from the nearby villages in the healthier foothills.3 3 Ziegler, “Malaria Landscapes,” 145, 143. The malarial nature of Rome and the surround- ing Agro Romano was the subject of intense study in the nineteenth century: See for example J. B. Michel, Recherches Médico-Topographiques sur Rome et L’Agro Romano (Rome, 1811); Francesco Puccinotti, Storia delle Febbri Intermittenti Perniciose di Roma (Napoli, 1838), 2 v.; Gabriele Taussig, The Roman Climate: Its Influence on Healthy and Disease, Serving as a Hygeienical Guide (Rome, 1870). Corrado Tommasi-Crudeli, The Climate of Rome and the Roman Malaria (London, 1892); W. North, Roman Fever (London, 1896). For information about malaria in Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/jinh_a_01302 by guest on 25 September 2021 400 | BENJAMIN REILLY Rome and its environs may have been chronically unhealthy for its own inhabitants, but many historians suspect that these places were even more dangerous for the countless pilgrims, litigants, dele- gates, traders, relic-hunters, and other sightseers who visited there between 500 and 1000. Llewellyn described early medieval Rome as a “death-trap, especially for unacclimatized visitors from the north.” His observation applied particularly well to foreign soldiers, who discovered that (as Godfrey of Viterbo quipped in 1167), “when unable to defend herself by the sword, Rome could defend herself by means of the fever.” Historians have noted that the German soldiers of the Holy Roman Empire who ventured to Rome were struck down by malaria with almost clockwork regularity. The ability of the Empire to control Rome was also hampered by the rapid deaths of no less than four German appointees to the papacy from 1048 to 1055 due to malaria.4 Nor did the problem of northern European vulnerability to Roman fevers seem to decline over time. According to Sallares, “all the literature on Malaria in early modern Rome states that adult immigrants or visitors were more vulnerable than people who had been born and had lived all their lives in Rome.” Nicolas Rome and its environs during antiquity and late antiquity, see W. H. S. Jones, “Dea Febris: A Study of Malaria in Ancient Italy,” Annals of Archaeology and Anthropology (1909), II, 97–124; Robert Sallares, Malaria and Rome: A History of Malaria in Ancient Italy (New York, 2002); David Soren, Malaria, Witchcraft, Infant Cemeteries, and the Fall of Rome (San Diego, 2002); Laura D. Lane, “Malaria, Medicine, and Magic in the Roman World,” in David Soren and Noelle Soren (eds.), A Roman Villa and a Late Roman Infant Cemetery (Rome, 1998), 633–651. The lacuna in evidence about malaria in Rome during the Middle Ages probably reflects the paucity of available source materials rather than any diminution of the disease risk. As Newfield notes, “With at least 25,000 inhabitants, a riverside setting, and a suitable climate, Rome had the greatest malarial potential in all of early modern Europe. One suspects had Gregory of Tours [an important source on malaria in France] lived in Rome the record would be well marked by intermittents” (Timothy P. Newfield, “Malaria and Malaria-Like Disease in the Early Middle Ages,” Early Medieval Europe, XXV [2017], 294–295). 4 Peter Llewellyn, Rome in the Dark Ages (London, 1971), 194; Godfrey re-quoted from Fiammetta Rocco, Quinine: Malaria and the Quest for a Cure That Changed the World (New York, 2003), 25. Krautheimer, Rome, 153; Thomas Hodgkin, Italy and Her Invaders (Oxford, 1880), I, 123; James Bryce, The Holy Roman Empire (London, 1871), 139.