Unformatted accepted version of: Mitchell, P.D. The spread of disease with the crusades. In:
Between Text and Patient: The Medical Enterprise in Medieval and Early Modern Europe.
Ed. B. Nance and E.F. Glaze. Florence: Sismel 2011, p.309-330.
The Spread of Disease with the Crusades
Piers D. Mitchell
Abstract: It has often been assumed that the crusades were responsible for the spread of
disease from the Middle East to Europe during the twelfth and thirteenth centuries.
However, there has actually been very little critical assessment of the evidence for such
potential tranmission. This analysis presents the evidence for the spread of infectious
disease in both directions between Europe and the Middle East, and also within
different regions of the Middle East, with the travels of crusaders and pilgrims.
Keywords: crusades, leprosy
«In the year of our Lord 1100, after achieving all their objectives in going to
Jerusalem, the nobles returned and reclaimed their own lands as was right»
. This return of
Orderic Vitalis, The Ecclesisatical History of Orderic Vitalis, ed. and trans. M. Chibnall, 6 vols,
1968-80, Oxford 1978, 6: 394-5 . «Anno ab incarnatione Domini MoCo peractis rebus pro quibus Ierusalem
ierant optimates redierunt, et sua ut iustum erat repetierunt».
crusaders to Europe has frequently been blamed by modern authors for the spread of disease
Sometimes it has been suggested that the transfer was for the first time, while others
acknowledge pre-existence of a disease in Europe before the crusades, but feel a new
epidemic resulted from the fresh introduction. Claims for specific diseases spread in this way
include outbreaks of smallpox
, influenza and leprosy
, the eye disease
, parasitic worms such as bilharzia
and animal carriers of disease such as the black
Perhaps the best known historical example of the spread of disease with exploration
and conquest was a consequence of the transatlantic sea voyages of Christopher Columbus
and others in the late fifteenth and sixteenth centuries. Diseases thought to have been
introduced to the Americas at that time include measles, smallpox, diptheria, malaria and
. Since the concept of cultural exchange between Europe and the Middle East with
the crusades is well accepted
, it is not unreasonable to suggest that there would also have
been a biological exchange of microorganisms there too. Medieval travelers were certainly
C. Costello, «Ireland and the crusades», The Irish Sword 9 (1070), 263-77; J.-N. Biraben, «Diseases
in Europe: equilibrium and breakdown of the pathocenosis» in Western Medical Thought from Antiquity to the
Middle Ages,ed. M.D. Grmek and B. Fantini, trans A. Shugaar. Cambridge (MA) 1998, 319-53, esp. 348-9.
H. Zinsser, Rats, Lice and History London 1985, 125.
P. Hastings, Medicine: an International History, London 1974, 35.
E. H. Hudson, «Treponematosis and pilgrimage», The American Journal of the Medical Sciences 246
A. Castiglioni, A History of Medicine. 2nd edition, trans. E.B. Krumbhaar, London1947, 353.
G. Cornand, « Trachome et armées», Revue Internationale du Trachome et de Pathologie Oculaire
Tropicale et Subtropicale 56 (1979), 99-110.
J.-P. Nozais, «The origin and dispersion of human parasitic disease in the Old World (Africa, Europe
and Madagascar)», Memorias Instituto Oswaldo Cruz 98 (suppl.1) (2003), 13-19.
F.E. Loosjes, «Is the brown rat (Rattus Norvegicus Berkenhout) responsible for the disappearance of
plague from Western Europe?», Documenta de Medicina Geographica et Tropica 8 (1956), 175-8.
C.S. Larsen, «In the wake of Columbus: native population biology in the post-contact Americas»,
Yearbook of Physical Anthropology 37 (1994), 109-54; C.S., Larsen, G.R. Milner, (eds) In the Wake of Contact:
Biological Responses to Conquest, New York 1994.
aware of the health risks associated with long arduous journeys. In consequence, regimens of
health were written to give advice on how to minimise the risk of disease. For example,
Adam of Cremona wrote his Regimen iter agentium vel peregrinantium for Emperor
. Items covered included diet, sleep, camping, exercise, delousing, bathing,
bloodletting, sea sickness, and care of the feet. The Muslim pilgrims and soldiers in the
region would have had similar access to written advice on how to look after themselves, such
as the guide to health for pilgrims by Qusta Ibn Luqua.
As well as the risk of weapon injury
during battle or torture from falling into the wrong hands,
the risk of becoming sick on a
crusade or pilgrimage seems to have been understood by most medieval travelers.
There are also modern parallels for the spread of disease by armies invading the
Middle East. For example, the eye infection trachoma is known to have spread throughout
European troops stationed in Egypt during the Napoleonic wars and the First World War, and
been spread to other soldiers on their return
. Since trachoma is believed to have been
present in the Middle East since ancient times
, it is quite likely that crusaders would have
been exposed to this too. These examples highlight not only that disease spread does happen
V.P. Goss, C.V. Bornstein, eds., The Meeting of Two Worlds: Cultural Exchange Between East and
West During the Period of the Crusades, Kalamazoo 1986.
Adam of Cremona, Artliche Verhaltungsmassregeln auf dem Heerzug ins Heilige Land fur Kaiser
Friedrich II, Geschrieben von Adam v. Cremona (ca.1227), ed. F. Honger, Borna-Leipzig 1913.
Qusta ibn Luqua, Medical Regime for the Pilgrims to Mecca: the Risala fi Tadbir Safar al Hajj,ed.
G. Bos, Leiden 1992.
Mitchell, P.D., Nagar, Y., Ellenblum, R. Weapon injuries in the 12th century crusader garrison of Vadum
Iacob castle, Galilee. International Journal of Osteoarchaeology 16 (2006) 145-55; Mitchell, P.D. The torture
of military captives during the crusades to the medieval Middle East. In: Noble Ideals and Bloody Realities:
Warfare in the Middle Ages, 378-1492. ed. N. Christie and M. Yazigi. Leiden, 2006, 97-118.
J. Vetch, An Account of the Ophthalmia which has Appeared in England Since the Return of the
British Army from Egypt, London 1807; A.F. MacCallan, Trachoma and its Complications in Egypt, Cambridge
1913, 2; J.W. Barrett, The Australian Army Medical Corps in Egypt, 1914-1915, London 1918, 92-5.
frequently, but also that it could be a major cause of social disruption to past societies. Such
disruption may result from acute deaths of key members of a community, chronic illness
among the workforce, or mass flight from epidemics
. The social response to epidemic
disease in the medieval period seems to have been both variable and complex
However, it needs to be remembered that at the time of the crusades, not all disease
was necessarily spread as a result of crusading activity. For example, Henry of Huntingdon
recorded how Alexander bishop of Lincoln fell ill while visiting Pope Eugenius at Auxere in
France in August 1147. We hear, «from the extraordinary heat of the weather the seeds of a
low fever were sown in his constitution, and he brought it with him to England. Shortly
afterwards he fell into a state of infirmity and langour, which ended in death»
. While the
crusades may well have been the predominant reason for the mass migration of peoples
during the twelfth and thirteenth centuries we must be careful not to blame the crusades for
every example of disease spread, as this was clearly not the case. It can only have been one
component of the bigger picture, along with pilgrimage within Europe, trade, and military
Many infectious diseases were endemic in Europe and the Middle East in the
medieval period, with their symptoms descibed in written texts and the pathological changes
A. Feigenbaum, «Archaeological evidence of the occurrence of regular seasonal ophthalmias in
ancient Egypt», Janus 46 (1957), 165-72.
J.W. McGrath, «Biological impact of social disruption resulting from epidemic disease»,. American
Journal of Physical Anthropology 84 (1991), 407-19.
D.W. Amundsen, «Medical deontology and pestilential disease in the late Middle Ages», Journal of
the History of Medicine and Allied Sciences 32 (1977), 403-21.
Henry of Huntingdon. Historia Anglorum: the History of the English, by Henry, Archdeacon of
Huntingdon, from A.C.55 to A.D.1154, ed. T. Arnold, London 1879, 280; Henry of Huntingdon, Chronicle, ed.
to the bones recovered with archaeological excavations
. Certainly the basic requirements
for the spread of infectious disease were present in the medieval Mediterranean world,
namely sufficiently large population size, poor hygiene, overcrowding, insufficient food, and
close contact with animals that also harbour infections
. In consequence, it is to be expected
that many of the participants of any crusade or pilgrimage may have traveled with an illness
of some kind. It is often very difficult to tell from the written sources exactly which disease
was present in each particular example in the past.
This is frequently because little detail of
the symptoms and signs of illness was recorded. In consequence, it is not my intention to
attempt to reconstruct the complexity of medieval infectious disease here. However, fevers
and epidemics are commonly described in medieval sources. We would expect that by far the
most common cause of fever in the medieval period would have been infection. What I do
attempt here is to determine whether transmissible diseases were spread with the crusades,
and whether there is any evidence that a change in the epidemiology of medieval health came
about as a result. After discussing the nature of the sources that record episodes of disease
spread, the examples are presented in three groups. The first is the spread of disease from
Europe to the Middle East with embarking crusaders and pilgrims, the second is the spread
by travel within the Middle East, and the third is the transfer of disease from the Middle East
to Europe with returning crusaders and pilgrims. Other approaches that might be used to
and trans. T. Forrester, London 1853, 285. «sed ex intempestiva caloris nimietate seminarium languoris attulit
in Angliam; unde mox infirmitati, deinde languori, tandem morti succubuit».
Biraben, «Diseases in Europe»; C.A. Roberts , M. Cox, Health and Disease in Britain: from
Prehistory to the Present Day, Stroud 2003.
T. McKeown, The Origins of Human Disease. Oxford 1988, 48.
explore the changing patterns of disease are then considered for one particular chronic
infectious disease well known in the medieval period, that of leprosy.
Interpreting the Sources
The textual sources that provide the evidence for disease spread at the time of the
crusades are not those written by medical practitioners. The wealth of examples that do exist
all come from non-medical authors.
This may be a result of the type of person who chose to
write down their experiences during a crusade or pilgrimage. The literary interests of a
medical practitioner while on crusade may well be to work on their medical text rather than
write a historical record of their expedition, as a respected medical text bearing their name
would further their career.
The heterogenous nature of the sources, together with their genre
as crusade texts, raises a number of challenges
. Chronicles were written by crusaders that
detailed the events on a particular military expedition to the East, and they often recorded
notable events such as epidemics or illness among their leaders. In early crusades these
authors were usually clerics (e.g. Albert of Aachen) but from the late twelfth century secular
authors were also at work (Ambroise, John of Joinville). Such sources often give a
P.D. Mitchell, «The use of historical texts for investigating disease in the past». International Journal of
Paleopathology (in press).
The authors quoted during this article are mentioned in this section to highlight where they fit into this genre,
with the full references given later.
Mitchell, Medicine in the crusades, 11.
S. Edgington, «Albert of Aachen and the Chansons de Geste» and J. France, «The anonymous Gesta
Francorum and the Historia Francorum qui Ceperunt Iherusalem of Raymond of Aguilers and the
Hierosolymitano Itinere of Peter Tudebode: an analysis of the textual relationship between primary sources for
the First Crusade», in: The Crusades and their Sources,ed. J. France and W.G. Zajac, Aldershot 1998, 23-37,
39-69; J.A. Brefold, A Guidebook for the Jerusalem Pilgrimage in the Later Middle Ages: a Case of Computer-
fascinating viewpoint, but may not, of course, be entirely balanced or representative for the
entire army. For example, different European subgroups took part on crusades, and an author
may have written unsympathetically about their home town’s enemies, and sympathetically
about their allies. Furthermore, some of these crusade chronicles were written by
eyewitnesses (Ambroise, John of Joinville), but others were written back in Europe by
summarising the accounts of other eyewitnesses (Albert of Aachen, Matthew Paris), and a
number constructed their works entirely from other written accounts. In peacetime many
pilgrims wrote accounts of their travels in the Holy Land. Christian examples were often
clerics, rather than secular authors, but Muslim pilgrims also recorded their travels, as in the
case of Ibn Jubayr. Some pilgrims vividly recounted their own experiences, but others
reproduced the itinerary and descriptions of earlier pilgrim accounts without making this
. A number of histories were written describing events within the Frankish States of the
Latin East. Some of these cover a short period of just a few decades (William of Tyre), but
others, like Orderic Vitalis, covered several centuries. In consequence, we have to be mindful
that the events described may not be accurate if they took part many years before the time of
writing, or even before the author was born. As before, some were written in the Latin East
(William of Tyre) while others were constructed in Europe largely from the written sources
of others (Orderic Vitalis). With these factors in mind, I have tried my best only to include
examples below that appear to represent genuine events at the time of the crusades. However,
Aided Criticism, Hilversum 1994; C.W. Grocock, and J.E. Sidberry, eds., The Historia Vie Hierosolimitanae of
Gilo of Paris and a Second Anonymous Author, Oxford 1997, xiii-xxiv.
J. Wilkinson, J. Hill, W.F. Ryan, Jerusalem Pilgrimage, 1099-1185, London 1988, 2.
I do appreciate that there will always be differences of opinion among modern historians as to
how accurate different sections of each text may really be.
Disease Spread to the Middle East
There are many examples of pilgrims who picked up illnesses as they traveled, and if
infectious, they presumably spread it to others as they moved on. Matthew Paris wrote in his
Chronica Majora of the notable events that ocurred in 1241.
Among the English nobles who died in this year were William de Forbes, Earl of Albemarle
who, when on his pilgrimage, was taken ill in the Mediterranean sea, and being unable to eat,
endured protracted sufferings for eight days; and on the Friday next before Easter, on which
day Christ on the cross resigned his spirit to his father, he, in a like manner, resigned his spirit
While we cannot tell whether this example was an infectious disease or not, it does illustrate
how a sick man continued to travel until he died from the illness.
Trade was responsible for merchants traveling huge distances, and sick merchants
would clearly have taken their diseases with them. The chronicler William of Tyre mentioned
how Egypt and Syria were the goal of traders from a huge area of Asia and Africa.
«Whatever our part of the world lacks in the way of spices, pearls, oriental treasures and
foreign wares is brought here from the two Indies, Saba, Arabia and both Ethiopias, as well
Matthew Paris, «Monachi Sancti Albani», in Chronica Majora ed. H.R. Luard, 7 vols., London
1877, IV, 174; Matthew Paris, English History from the Year 1235-1273 trans. J.A. Giles, 3 vols., London
1852, I, 391: «De magnatibus autem Angliae Willelmus de Fortibus, comes de Albamarla, in mari
Mediterraneo peregrinans, cum nullo modo posset comedere et octo diebus jejunando martirium protelasset,
die Veneris proxim ante Pascha, qua Christus in cruce Patri Suo spiritum, suum similiter Christo resignavit».
as from Persia and other lands nearby»
. Slavery was another method by which diseases
might be moved from one region to another. Tartar, Russian, Mongolian and sub-Saharan
African slaves are documented as for sale in many parts of the Mediterranean during the
Archaeology has also provided evidence for the spread of parasites from Europe to
the Middle East at the time of the crusades. In the twelfth and thirteenth centuries the Order
of St. John had a large complex at Acre, within the Kingdom of Jerusalem. This included an
impressive latrine block built on several floors, with thirty-five stone seats and a flushing
Analysis of latrine soil from the basement of these latrines has identified
the eggs of parasitic worms that infected the intestines of those who used the latrines in
crusader times. Eggs of the roundworm, whipworm and fish tapeworm were present
fish tapeworm was an unexpected find, as it has not been identified in earlier latrines from the
Middle East, and is not found in the region today. However, it is a common find in latrines
from northern Europe during the medieval period, particularly in Britain, northern France,
William of Tyre, Guillaume de Tyr: Chronique, ed. R.B.C. Huygens, 2 vols., Brepols 1986, II, 903;
William of Tyre. A History of Deeds Done Beyond the Sea, trans. E.A.Babcock, A.C. Krey, 2 vols., New York
1943, II, 336. «Ad hec ex utraque India, Saba, Arabia, ex utraque etiam nichilominus Ethiopia, sed et de
Perside et aliis adia centibus provinciis quicquid aromatum, margaritarum, gemmarum, Orientalium gazarum
et peregrinarum mercium».
B. Arbel, «Slave trade and slave labor in Frankish Cyprus (1191-1571)», Studies in Medieval and
Renaissance History 14 (1993), 149-90.
P.D. Mitchell, J. Huntley, E. Sterns, «Bioarchaeological analysis of the 13th century latrines of the
crusader hospital of St. John at Acre, Israel», in: The Military Orders: volume 3. Their History and Heritage,
ed.V. Mallia-Milanes, W. Zajac, Aldershot 2008; D. Syon, E. Stern, P. D. Mitchell, «Water installations at
crusader ‘Akko», ‘Atiqot (in press).
P.D. Mitchell, E. Stern, «Parasitic intestinal helminth ova from the latrines of the 13th century
hospital of St. John in Acre, Israel», in: Proceedings of the XIIIth European Meeting of the Paleopathology
Association, Chieti, Italy, ed. M. La Verghetta, L. Capasso, Teramo 2001, 207-13.
Germany and Scandinavia
. It is contracted by eating uncooked fish (perhaps smoked or
salted) that contain the parasite’s intermediate stages in its body. It seems very likely that the
fish tapeworms were transported to the Middle East in the intestines of crusaders from
northern Europe, who then used the latrines of the Order of St. John at Acre.
The fact that the fish tapworm has not become endemic in the Middle East is an
important one. Transfer of a transmissible infection or parasite to a new geographical region
will only lead to its establishment there if the new environment is compatible with its life
cycle. Since the fish tapeworm never took hold in the Middle East, it is likely that the region
was not compatible with at least one part of the worm’s life cycle. For example, the warmer
temperature of the lakes and rivers of the Middle East compared with northern Europe may
well have interrupted the waterborn part of the life cycle, as the species of snail and fish (both
intermediate hosts) that live there would have been different. This highlights how a disease
might be spread by the crusades, but be unable to survive in the new environment. The
consequence is that the spread will have no impact upon the epidemiology of that disease.
Disease Spread Within the Middle East
Infectious diseases present in the Middle East do appear from archaeological evidence
to have been a significant cause of death before, during and after the time of the crusades. A
comparison of child health at a twelfth century farming village and castle in the crusader
B. Hermann, «Parasite remains from medieval latrine deposits: an epidemiologic and ecologic
approach», in Actes des 3êmes Journées Anthropologiques, Notes et Monographies Techniques no. 24, Paris
kingdom of Jerusalem has shown significant differences in the life expectancies
crusader castle of Vallis Moysis was located to the south east of the Dead Sea, in modern
Jordan, while the Templar farming village of Parvum Gerinum in Galilee lay to the west of
Lake Tiberias, in modern Israel. Analysis of the age at death from human skeletal remains
excavated from each site demonstrated that the children tended to die younger at the castle
than at the village. This suggests that the lifestyle at the village may have been healthier for
children. Comparison was made with modern studies of childhood disease in the poorest
developing countries today. This found an identical slope to the life expectancy graph
suggesting that broadly similar causes of death may be present in modern developing world
and medieval populations, which seems plausible. If this is the case, it would appear that the
major causes of death at the castle may have been premature birth, congenital defects,
difficult labour with birth asphyxia, and congenital infections. This is because most of the
child deaths occurred at fetal age or within one month of birth.
At the farming village many
of the children lived to an age where, in modern times, children die from infectious diseases
such as whooping cough, tetanus and measles
. While the children at the castle and village
died without firm evidence for their cause of death to be left on their bones, those deaths at an
age when modern children mostly die from infectious diseases does suggest that these
P.D. Mitchell, «Child health in the crusader period inhabitants of Tel Jezreel, Israel», Levant 38
C.J.L. Murray, A.D. Lopez, The Global Burden of Disease, Boston 1996, 175.
W. Moss, G.L. Darmstadt, D.R. Marsh, R.E. Black, M. Santosham, «Research priorities for the
reduction of perinatal and neonatal morbidity and mortality in developing country communities», Journal of
Perinatology 22 (2002), 484-95.
Murray and Lopez, Global Burden, table 5.3; M.D. Seear, Manual of Tropical Pediatrics,
Cambridge 2000, 7.
infectious diseases were a significant cause of death in crusader times as well.
There are fewer textual examples of possible disease spread within the Middle East
during the crusades than is the case for spread to and from Europe and the Middle East.
However, this may be due in part to the fact that many more texts discussed travels between
Europe and the Middle East than discussed movements within the Middle East itself. One
example that we do have was Frederick the Archbishop of Tyre. The chronicler William of
Tyre probably wrote about this in his history since Frederick was his predecessor as
archbishop of that city. Frederick contracted dysentery while participating in a crusade
against Egypt in 1167, led by King Amaury of Jerusalem. «He began to suffer from a
dangerous attack of dystentery caused by drinking the water of the Nile, and his illness
increasing, he was forced to return home [to Tyre] before Alexandria was surrendered to the
. Dysentery is a disease that is often mentioned in passing in crusader period sources.
For example, members of the Order of the Temple who contracted dysentery were nursed
apart from those with other diseases in the order’s infirmaries on account of the unpleasant
noise and smell.
Recent archaeological analysis has determined the types of dysentery
present in the Middle East at the time of the crusades. The headquarters of the Order of St.
John in the Kingdom of Jerusalem during the late twelfth and thirteenth centuries was located
in the city of Acre. The latrines of this complex have been excavated, and the soil
William of Tyre, ed. Huygens, II, 903; William of Tyre, trans. Babcock, II, 337: «sed aquis Niliacis
causam prestantibus dissinteria cepit periculosissime laborare, unde antequam domino regi traderetur coactus
est, invalescente egritudine, domum redire».
Mitchell, P.D. The infirmaries of the Order of the Temple in the medieval kingdom of Jerusalem. In: The
Medieval Hospital and Medical Practice: Bridging the Evidence. Ed. B. Bowers, Aldershot 2006, 225-34.
radiocarbon dated and analysed. Along with the eggs of a range of human interstinal parasitic
worms, the organisms that cause dysentery were discovered.
The species present were
Entamoeba histolytica and Giardia duodenalis. It seems likely that Archbishop Frederick
may well have contracted one of these two organisms while in Egypt. This is a good example
of someone who travels to Egypt, contracts a transmissible infectious disease, and returns to
Tyre while still suffering with the illness.
A further example of probable disease spread within the Middle East took place
around eighty years later. At the close of the Seventh Crusade, King Louis IX of France left
Egypt with his defeated armies in 1250. The campaign in Egypt was severely effected by
dysentery and other illnesses recorded in the chronicles
, so many of the soldiers were still
ill when they left. The French fleet headed for Frankish Acre. King Louis was accompanied
by John of Joinville, who described an epidemic there shortly after they arrived at Acre. He
I succumbed, and all my people too, to a continual fever which forced me to take to my bed;
there was never a day all that time on which I had anyone to help me or lift me up. I felt that
only death awaited me, from a sign that was constantly close to my ear; for there was no day
on which twenty or more dead were not carried to the church, and from my bed, as each was
carried in, I heard the chant of Libera me, Domin.
Mitchell, P.D., Stern, E., Tepper, Y. Dysentery in the crusader kingdom of Jerusalem: an ELISA analysis of
two medieval latrines in the city of Acre (Israel). Journal of Archaeological Science 35 (2008), 1849-53.
John of Joinville, Histoire de Saint Louis: Jean Sire de Joinville,ed. N. de Wailly, Paris 1874, 6;
John of Joinville, The Life of Saint Louis, ed. N. de Wailly, trans. R. Hague, London 1955, 24.
John of Joinville, Histoire de Saint Louis, 226; John of Joinville, The Life of St Louis, 129. «Or avint
ainsi que une centenue me prist, par quoy j’alai au lit, et toute ma mesnie aussi. Ne onques un jour toute jour je
n’oy onques qui me peust aidier ne lever; ne je n’atendoie que la mort, par unsigne qui m’estoit delez l’oreille:
car il n’estoit nus jours que l’on n’aportast bien vingt mors ou plus ou moustier; et de mon lit, toutes les foiz
que on les aportoit, je ousie chanter, Libera me, Domine».
The epidemic that Joinville recorded may have occurred from one of two causes, and
interpretation does rather depend upon just what this unidentified disease was. One
possibility is that the sick crusaders from Egypt spread it on arrival to the water supply or the
mosquitos of Acre, which resulted in a new outbreak of the disease. A second possibility is
that a disease already present in Acre found little resistance among the weakened new
arrivals, and so an epidemic was triggered.
Disease Spread from the Middle East to Europe
There were a great many recorded examples of crusaders and pilgrims contracting
illness once they arrived in the east. While many died from these illnesses, and others fully
recovered before their journey home, a proportion would still have been ill when they
returned to Europe and so potentially spread the disease to there. Albert of Aachen wrote an
account of the first crusade, from 1097-99, based on the accounts of returning crusaders and
written works of other eye-witnesses. In 1098, after the city of Antioch had been captured by
the crusaders, we hear that
a plague of most severe mortality happened in the city of Antioch ... this very severe plague
grew more widespread and serious, and it began to diminish by death the Christian army to
such an extent that for six months scarcely a day dawned but a hundred, or fifty, or thirty at
least gave up the ghost
Another such example comes from a century later. During the Fourth Crusade to
Albert of Aachen, Historia Ierosolimitana: History of the Journey to Jerusalem, ed and trans. S.B.
Edgington, Oxford 2007,342-3.
Constantinople (1203-4), a crusade fleet arrived at Acre in early summer 1203. Gunther of
Pairis wrote how Abbot Martin, his eye witness source, experienced an epidemic there first
That summer, during those days which, because of the wickedness of the heat we call «dog
days», a very serious epidemic broke out, and the human mortality rate was so great that
more than two thousand corpses are said to have been buried in one day. Moreover, the
plague attacked so swiftly and unexpectedly that whoever began to feel ill could, most
certainly, expect to be dead within three days.... The pestilence pervaded the city and its
environs for quite a while. As a result, a majority of Acre’s citizens and the pilgrims pausing
there were carried off by the corruption of the contagion. For example, of the sixteen persons
dwelling in the abbot’s hospice, four barely escaped death. All the others fell victim to the
peril. But even those who survived, as if they had accepted the answer of death, awaited it
every single moment, languid and drawn.
Having demonstrated that arriving crusaders were
at risk of contracting epidemic diseases on their arrival in the east, we are in a position to
identify evidence for their travel and the potential spread of their illness.
Sometimes we have direct evidence for crusaders deciding to return home early on
account of their newly acquired illnesses, in order to try and get better. This of course may
have acted as a source of disease spread. Richard de Templo was an Augustinian prior from
London who wrote an account of the Third Crusade based upon the the stories of returning
English crusaders and other eyewitness chronicles such as Ambroise. He described how large
numbers of crusaders besieging the city of Acre became ill during the siege, which lasted a
Gunther of Pairis, Hystoria Constantinopolitana: Untersuchung und Kritische Ausgabe, ed. P. Orth,
Hildesheim 1994, 131-3; Gunther of Pairis, Hystoria Constantinopolitana: The Capture of Constantinople, ed.
and trans. A.J. Andrea, Philadelphia 1997, 86-7: «Eadem estate circa dies illos, qui propter fervoris maliciam
caniculares vocari solent, orta est ibi gravissima pestis et coporum humanorum corrupcio in tantum, ut una die
plus quam bis mille corpora mortuorum sepulta memorentur. Erat autem tam subita et improvisa lues, ut
quisquis cepisset egrescere, infra triduum mortem certissimus expectaret….Hac igitur peste in civitate illa et
finibus eius diu pervagante maxima pars tam civium quam peregrinorum ibidem commorancium eiusdem
contagionis tabe consumpta est. Nam et de sedecim hominum personis, que in abbatis hospicio versabantur, vix
ipse quartus mortem effugit, ceteri omnes periculo succubuerunt, sed et hi qui superstites erant, quasi responso
mortis accepto languidi et exsangues eam per singula momenta certissime prestolabantur».
year and a half. Some of the soldiers found the conditions too much to bear, and decided to
go home. These included Ludwig III, the landgrave of Thuringia in Germany. «The
landgrave had become unwell and deserted the camp to return to his own country»
King Philip of France is also known to have become ill during the Third Crusade,
with what appears to have been an infectious disease. In the seige of Acre in August 1191, he
«fell very ill from a double tertian fever»
. William le Breton was a contemporary writing
back in Europe. He wrote,
Philip lay sick in Acre attended by a few followers; for he was taken with a fierce fever and
frequent tremblings. Such violent irritation, so fierce a heat, laid waste his bones and all his
limbs that every nail fell off his fingers and all the hair from his brow... and since he could
not be entirely healed where he was, on the kindly advice of his nobles and leeches he
became eager to return to his own land
Since Philip was a king he could employ his own chroniclers to write of his desire to return
home in a more favourable light than was the case for the «deserting» landgrave of
Most crusaders seemed to have completed their campaign and returned home without
such accusations of desertion lingering over their heads. However, a proportion of these were
Richard de Templo, Itinerarium Peregrinorum et Gesta Regis Ricardi, ed. W. Stubbs, London 1864,
94; Richard de Templo, Chronicle of the Third Crusade: a Translation of Itinerarium Peregrinorum et Gesta
Regis Ricardi, trans. H. Nicholson, Aldershot 1997, 99 «Landegravus enim valetudinarius effectus repatriandi
praetextu castra deseruit».
Continuation of William of Tyre. La Continuation de Guillaume de Tyr (1184-1197), ed. M.R.
Morgan, Paris 1982, 131; in: The Conquest of Jerusalem and the Third Crusade: Sources in Translation, ed.
M.R. Morgan, trans. P.W. Edbury, Aldershot 1996, 11-145, esp. 108-9.
William the Breton, Philippide: Oeuvres de Rigord et de Guillaume le Breton, Historiens de
Philippe Auguste, ed. H.F. Delaborde, 2 vols, Paris 1885, II, 106 «Solus cum paucis hec inter agenda Philippus
febre gravi tactus, crebroque tremore fatiscens, infirmabatur, Acharonque jacebat in urbe; tantaque scaturies,
tantus calor illius ossa totaque membra fuit ita depopulatus, ut omnes a digitis ungues caderent, a fronte
chronically ill by this stage. The jongleur Ambrose recorded his observations while on the
Third Crusade, from 1189-92. He described how many of the crusaders became ill or died
from sickness during the expedition. At the close of the crusade in 1192, many of the
participants returned to Europe by sea, and a good number were still not healthy. He
mentions how, «some fell sick, nor ever were made whole»
. Some never survived the
journey, but presumably may have spread their illness at ports where they stopped on the
way. A good example from a later crusade was that of the Count of Brittany. John of Joinville
mentions that at Easter 1250 sections of King Louis IX’s crusading army left Egypt and set
sail for Europe. Many of these still appear to be suffering with the dysentery, scurvy and
tertian malaria (double terceinne) that were so often described in the chronicle. We hear that,
«they embarked accordingly and went back to France, taking with them the good Count
Perron of Brittany, who was so ill that he survived only three weeks and died at sea»
Of course many of the sick crusaders did survive the journey, and it is these that
might conceivably have been most to blame for the spread of any diseases. At the close of the
Third Crusade in Autumn 1192, Richard de Templo wrote of these chronically sick returning
soldiers that did reach home. «Other were infected by incurable disease and never regained
capilli;….cumque nequiret ibi sanari prorsus, amico Hortatu procerum, cum consilio medicorum in patriam
statuit nativaque rura redire».
Ambroise. Estoire de Guerre Sainte: Histoire en Vers de la Troisième Croisade (1190-1192),ed.G.
Paris, Paris 1897, 327, line 12211-2; Ambroise. «The History of the Holy War», in Three Old French
Chronicles of the Crusades, ed. G. Paris, trans. E.N. Stone, Washington: 1939, 1-160, esp. 158: «e li auquant,
s’i engroterent, si que onques n’en respasserent».
John of Joinville, Histoire de Saint Louis, 206; John of Joinville, The Life of Saint Louis, 119. «En
lour galies monterent et s’en vindrent en France, et en amenerent avec aus le bon conte Perron de Bretaingne,
qui estoit si maladies que il ne vesqui puis que troiz semainnes, et mourut sus mer».
their health, even in their homeland»
. There are a number of examples in the chronicles that
highlight this. For example, Hugh of Chaumont-sur-Loire was a sick man when he returned
to France at Eastertime 1100, following his participation in the First Crusade
Bertrand of Bas, a canon of Le Puy, fell ill at sea on his way home from the First Crusade.
John of Joinville’s chronicle of the Seventh Crusade (1249-52) devotes considerable detail to
the hardships of life in the army camp, and especially the diseases from which they suffered.
The majority of the army seems to have contracted dysentery (menoison mout fort), and the
king’s diarrhoea was so bad that part of his trousers had to be cut away to allow it to run
. Modern research has shown that while most people who survive dysentery are cured of
the disease, a proportion become chronic carriers that excrete the parasites in their faeces
every time they go to the toilet
. When they returned home this may have put others in their
housholds and towns at risk of contracting dysentery, if they had not had the disease
It was not just crusaders who traveled across the Mediterranean at the time of the
crusades. Thousands of pilgrims and merchants did too, and their ships sailed from coastal
ports such as Acre and Caesarea to Italy and southern France. These would obviously have
acted as a potential method via which diseases may have been spread. The Muslim pilgrim
Richard de Templo, Itinerarium Peregrinorum, 439; Richard de Templo, Chronicle of the Third
Crusade, 379: <alii morbo incurabili corrupti, nunquam postea convaluerunt vel in patria>.
Hugh of Chaumont-sûr-Loire, «Gesta ambaziensium dominorum», in Chroniques des Comtes
d’Anjou et des Seigneurs d’Amboise, ed. L. Halphen, R. Poupardin, Paris 1913, 102.
Bertrand of Bas, Cartulaire de Chamalieres-sûr-Loire en Velay, ed. A. Chassaing, Paris 1895, 54:
«gravatus infirmitate nimia super mare».
John of Joinville, Histoire de Saint Louis, 6; John of Joinville, The Life of Saint Louis, 24.
Ibn Jubayr recorded how he boarded a ship at crusader Acre in 1184, bound for Sicily. He
mentions that early on in the voyage just a few passengers died, but then the numbers
increased dramatically. «Two Muslims died, God have mercy on them. They were thrown
into the sea. Of the (Christian) pilgrims, two died also, and then were followed by many»
Since he details the wide range of food and drink on board, it seems unlikely that hunger or
thirst was the cause for these deaths. In the circumstances it is probable that an epidemic of
infectious disease had broken out. This ship appears to have been an example of how pilgrim
traffic was also able to transmit infectious diseases from the Middle East to Europe by sea.
The Long-term Impact of Disease Spread in Europe: The Case of Leprosy
Clearly sick people were travelling in different directions across the Mediterranean
sea at the time of the crusades. While there are good descriptions of outbreaks of epidemics
breaking out after a ship docked, it is also interesting to consider whether chronic diseases
were similarly spread. If they were spread, then we must ask whether this had enough of an
impact to alter the epidemiology of disease in medieval Europe
. There might in theory be
evidence for new diseases being introduced to certain parts of Europe, or a rare disease might
become common after a large number of people arrived with that disease. It is not easy to
assess such a theory for a number of reasons. Applying modern approaches such as statistical
J. Blessman, I.K. Ali, P.A. Nu, B.T. Dinh, T.Q. Viet, A.L. Van, C.G. Clark, E. Tannich,
«Longitudinal study of intestinal Entamoeba histolytica infections in asymptomatic adult carriers», Journal of
Clinical Microbiology 41, no. 10 (2003), 4745-50.
Ibn Jubayr, The Travels of Ibn Jubayr, ed. and trans. R.C.J. Broadhurst, London 1952, 329.
Biraben, «Diseases in Europe».
comparison of disease prevalence requires an accurate diagnosis of the disease under
investigation, and accurate data on how common that disease was in different time periods or
different locations. Textual sources from the time of the crusades rarely give us such
information. However, I have previously explored some sources of relevant information for
one of the major chronic infectious diseases of medieval times, that of leprosy
. We might
expect that the findings could be relevant for other chronic infectious diseases in Europe too.
A number of medical historians have claimed that crusaders caught leprosy while in
the east and brought it back with them to Europe, increasing the prevalence of the disease to
what some term an epidemic.
Such repetition of this theory might suggest that it is well
accepted, and indeed there is some evidence that at first glance would appear to be
compatible with this theory. Leprosy is known to have been present in the Middle East before
the time of the crusades, as archaeological examples there date back to the Roman and
Certain key figures living in the Frankish states of the Latin East are
known to have developed leprosy, with clear descriptions of their symptoms in written texts.
Perhaps the best known example was King Baldwin IV of Jerusalem, who lived in the 1170s-
P.D. Mitchell, «The myth of the spread of leprosy with the crusades», in The Past and Present of
Leprosy: Archaeological, Historical, Palaeopathological and Clinical Approaches, ed. C.A. Roberts, M.E.
Lewis, K. Manchester, Oxford 2002, 171-7.
D.A. Zambaca Pasha, Le Lèpre a Travers les Siècles et les Contrées Paris 1914, 97; J. Harrington,
The School of Salernum, London 1920, 7; Castiglioni, A History of Medicine, 353; R.M. Clay, The Mediaeval
Hospitals of England, London 1966, 36; M. Foucoult, Madness and Civilization: a History of Insanity in the
Age of Reason, trans. R. Howard, London 1967, 6; S.R. Ell, «Pilgrims, crusades and plagues», in Health and
Disease in the Holy Land, ed. M. Waserman and S.S. Kottek New York 1996, 185; Biraben, «Diseases in
J.E. Molto, «Leprosy in Roman Period skeletons from Kellis 2, Dakhleh, Egypt», in The Past and
Present of Leprosy: Archaeological, Historical, Palaeopathological and Clinical Approaches, ed. C.A. Roberts,
M.E. Lewis, K. Manchester, Oxford 2002, 183-96; J. Zias, «Leprosy and tuberculosis in the Byzantine
. Indeed, the military order of St. Lazarus was established in Jerusalem shortly after the
first crusade to allow crusaders and pilgrims with the disease to live together but still fight
with the main crusader army
. In this context, it would not be unreasonable if crusaders were
exposed to the disease and some might contract the illness and return to Europe with it. Many
human skeletons showing the changes of leprosy have been excavated from cemeteries in
medieval Europe, confirming its presence there
. At the time of the crusades a large number
of leprosaria were built in Europe, to house people with leprosy. Many new laws were passed
in both Europe and the Latin East that dealt with the diagnosis, segregation, and social
position of leprosy patients
. The amount of information on leprosy found in medical texts
had increased during the medieval period too, if we compare the seventh century Paul of
Aegina with thirteenth century Theodorico Borgognoni, for example
. One interpretation of
this evidence has been that there was a dramatic rise in the prevalence of leprosy in Europe
during the twelfth and thirteenth centuries, concurrent with the crusades. In other words, the
crusades appear to have been responsible for an epidemic of leprosy in medieval Europ
However, under close inspection none of these findings really does suggest an epidemic of
monasteries of the Judean Desert», in Human Paleopathology: Current Syntheses and Future Options, ed. D.J.
Ortner, A.F. Aufderheide, Washington 1991, 197-9.
P.D. Mitchell, «An evaluation of the leprosy of King Baldwin IV of Jerusalem in the context of the
mediaeval world», in B. Hamilton, The Leper King and His Heirs: Baldwin IV and the Crusader Kingdom of
Jerusalem, Cambridge 2000, 245-58.
M. Barber,«The Order of Saint Lazarus and the crusades», The Catholic Historical Review 80
C.A. Roberts, M. Cox, Health and Disease in Britain: from Prehistory to the Present Day, Stroud
S. Shahar, «Des lepreux pas comme les autres: l’Order de Saint-Lazare dans le Rayaume Latin de
Jerusalem», Revue Historique 267 (1982), 19-41.
Paulus Aegineta, The Seven Books of Paulus Aegineta. trans. F. Adams, 3 vols., London 1846, II, 1-
5; Theodorich Borgognoni, «Cyrurgia», in: Cyrurgia Guidonis de Chauliaco, et Cyrurgia Bruni, Theodorici,
Rogerii, Rolandi, Bertapali, Lanfranci, ed. B. Locatellus, Venice 1498; Theodorich Borgognoni, The Surgery of
Theodorich, ca. AD 1267, trans. E. Campbell, J. Colton, 2 vols, New York 1960, 167-82.
leprosy in Europe at the time of the crusades. In fact, they all reflect changes in other aspects
of medieval life. The skeletal remains and textual descriptions of people with leprosy have
been found in Europe at least dating back to Roman times
, so it cannot be said to have been
newly introduced by the crusades. The prevalence of leprosy in cemeteries seems to have
gradually increased over the centuries to reach its peak in the medieval period, and there is no
sudden jump in prevalence in the early twelfth century to suggest that it became more
common purely due to returning crusaders
. Many leprosaria were built in the twelfth and
thirteenth centuries, but in many parts of Europe this started in the eleventh century, before
the crusades began. There is also a similar explosion in the number of hospitals being
founded, and graphs comparing such foundations show an extremely similar pattern of
foundations over time
. It became fashionable for wealthy nobles and landowners to found
leprosaria and hospitals in the eleventh to fourteenth centuries, as such charity would reflect
favourably on the founders during their lifetimes and give them the benefit of the occupants’
prayers for their souls opon their death
. A change, therefore, in the way the rich regarded
philanthropy, rather than a rise in the prevalence of all diseases, lead to the foundation of so
many hospitals and leprosaria in Europe at that time. The claim that leprosy was spread by
See note 57 above.
V. Mariotti, O. Dutour, M.G. Belcastro, F. Facchini, P. Brasili, «Probable early presence of leprosy
in Europe in a Celtic skeleton of the 4th-3rd century BC (Casalvecchio di Reno, Bologna, Italy)», International
Journal of Osteoarchaeology 15 (2005), 311-25. S. Mark, «Alexander the Great, seafaring, and the spread of
leprosy», Journal of the History of Medicine and Allied Sciences 57 (2002), 285-311.
Roberts and Cox, Health and Disease in Britain.
C.A. Roberts, «Leprosy and leprosaria in medieval Britain», M.A.S.C.A. Journal 4, no. 1, (1986), 15-
21; C. Rawciffe. Leprosy in Medieval England. Woodbridge 2006.
C. Rawcliffe, Medicine for the Soul: the Life, Death and Resurrection of an English Medieval
Hospital: St. Giles’s, Norwich, c.1249-1550, Stroud 1999; C. Rawcliffe, Leprosy in Medieval England,
the crusades is a modern one, in nineteenth and twentieth centiry works. It is not a concept
that I have ever come across in medieval works. Medieval Europeans do not appear to have
blamed their problems with leprosy on the crusades.
A number of medieval medical texts discuss leprosy in great detail, and an analysis of
the writings of several medical authors reveals increasing attention given to disease before
the crusades, both in the length of the author’s treatments, and in the proportion of their texts
devoted to leprosy. In modern times we would expect medical textbooks to devote significant
sections to those diseases that were most common or most serious, and restrict text on rare or
unimportant conditions to just small sections. If the same applies to medieval medical texts,
then such large sections might be significant to our argument. One of the earliest European
sources to describe leprosy was Aulus Cornelius Celsus (1st century BC Italy), and his entry
can be compared with Paul of Aegina (6th-7th century eastern Mediterranean) and academic
surgical texts from 13th century Italy such as Theodorico Borgognoni (13th century). Sections
that described the symptoms of leprosy as we understand them today were analysed, which
controlled for variation in the terminology used for the disease in different areas and different
time periods. To control for the possibility that later texts were just larger in size than earlier
texts, the number of words used in the sections on leprosy were also given as a percentage of
the number of words written about all skin diseases. Since Celsus and Theodorich wrote in
Latin and Paul wrote in Greek, is it important that the number of words is calculated from
versions of the texts in the same language, in case one language was more succinct than the
other, using fewer words to convey the same information. While the actual number of words
used will vary if other language editions are used, the proportions for each author will of
course remain the same if the same language is used for all.
The English language version of Celsus
has 250 words on leprosy, and this
represents just 2.5% of the total section on skin diseases. The English language version of
Paul of Aegina
has 2,000 words on leprosy and this represents 12% of his section on skin
diseases. The English language version of Theodorico Borgognoni
has 5,280 words on
leprosy, and this represents 39% of his section on skin diseases. If these three authors are
representative of the wider body of medical writing on leprosy and other skin diseases, then it
would seem that in the thousand years before the crusades, authors in the Mediterranean area
were gradually writing more on leprosy as the centuries went by. The increase respresents not
only more detailed descriptions of the symptoms and signs of the disease, but also more
information on the theory regarding its etiology, tests to aid diagnosis, and treatment options.
Leprosy also seems to have become a larger proportion of the total amount these authors
wrote on skin diseases. This would suggest that leprosy was either gradually becoming more
common or gradually perceived as more important over this time. The findings do not
suggest that the disease was very rare up to the eleventh century and then suddenly became
common, so this information does not support the theory of an epidemic of leprosy in
medieval Europe with the return of infected crusaders. It seems to have been getting more
Aulus Cornelius Celsus, De Medicina, trans. W.G. Spencer, 3 vols., London 1935, 343.
Paulus Aegineta, The Seven Books, 1846, II, 1-5.
Theodorich Borgognoni, Surgery, 1960, II, 167-82.
common in Europe by the time of the crusades anyway.
Whichever way we investigate this theory, there is no firm evidence for large
numbers of crusaders returning to Europe infected with leprosy and triggering an epidemic of
the disease there. It is hard to know for sure whether the same applies to other chronic
infectious diseases such as tuberculosis, brucellosis, or malaria as they are not as clearly
described as distinct entities in written texts and they did not trigger the foundation of
specific institutions to house people with these conditions. For those chronic infectious
diseases, however, where archaeological examples have been identified from Europe prior to
the time of the crusades, we must remain sceptical as to whether the crusades would have had
any impact upon the epidemiology of these diseases in medieval Europe.
Infectious diseases were certainly spread with the crusades. Many crusaders do appear to
have left the Holy Land suffering with a range of illnesses. Some died on the way home, but
the survivors may well have spread diseases to the people they met upon their return to
Europe. Certainly the transfer of epidemic diseases by crusader and pilgrim ships did
sometimes have profound effects when they docked, as records of the ensuing loss of life in
the townspeople were often quite marked. However, contrary to popular perceptions, this was
by no means a unidirectional phenomenon from the Middle East to Europe. There are clear
examples of crusaders setting out for the Middle East carrying diseases with them. Clearly a
proportion of these may have spread infectious diseases from Europe to the Holy Land.
There is no good evidence for the well-quoted theory that returning crusaders flooded
Europe with new diseases. Trade and invasions had been spreading disease around the
Mediterranean area and northern Europe for centuries before the time of the crusades. This
gave ample opportunity for the introduction to Europe of a wide range of infectious diseases.
Even if a crusader did head east and contract leprosy, the disease most often cited in this
context, the fact that leprosy was already endemic right across Europe by the twelfth century
means that the activities of this crusader would have had no real impact upon the
epidemiology of the disease in his home town or anywhere else. Similarly, a twelfth century
army camp in France or Italy would have been just as susceptible to dysentery or malaria as a
crusader army camp in Syria, since the diseases were already present in both regions prior to
the crusades. By the medieval period the only parasites endemic in the Middle East but not
Europe were species that could not be transmitted within Europe anyway, due to the colder
climate there (e.g dracunculiasis and bilharzia). If a disease was newly introduced to the
Middle East at the time of the crusades, then we might theoretically expect crusader shipping
to introduce it to the first time to Europe, but there were no clear examples of this occurring.
It seems likely that the crusades were responsible for the spread of particular, short lived,
epidemic outbreaks in both Europe and the Middle East. They were probably also responsible
for a proportion of crusaders contracting specific, chronic diseases or parasites while on their
expedition. However, I have been unable to find any good evidence to suggest that the
epidemiology of health and disease in Europe was in any way shifted by these returning
crusaders. This was because so many infectious diseases were ubiquitous in Europe already
by the medieval period.
Figure 1: Crusaders on board ship sailing to the Holy Land. London, British Library MS
Henry Yates Thompson 12, f. 58v. History of Outremer by William of Tyre, c. 1250-60.
Reproduced with the permission of the British Library.
Figure 2: Ovum of the fish tapeworm (Diphyllobothrium latum) recovered from a 13th
century latrine in the complex of the Order of St. John in Acre, Israel. Reproduced with the
permission of the Journal of Paleopathology.