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3-08-2015, 02:17

The Geography of Human Disease

The prevalence and distribution of diseases in subSaharan Africa have been determined by the natural environment, indigenous living patterns, and the interrelationships between African peoples and newcomers from other continents. The spread of agriculture since about 3000 B. C.; the extensive commercial contacts with the Moslem world from about A. D. 1000, and with Europe since the fifteenth century; and the establishment of colonial rule in the late nineteenth century - all have had important consequences for health conditions in Africa.

There is little evidence about the disease environment confronting Africans until fairly recent times. Literacy dates back to only about A. D. 1000, and then only in Ethiopia and some areas of the savanna zone just south of the Sahara desert. Written accounts of conditions on parts of the western and eastern coasts begin with the Portuguese voyages of the fifteenth and sixteenth centuries, but literary information on most of the vast interior is not available until well into the nineteenth century. Serious medical data collection really began with the colonial period, but even today knowledge of disease incidence and prevalence is far from adequate.

Africa south of the Sahara is a vast area with many different ecological zones. Besides the Sahara itself, there are extensive desert regions in the Horn of northeastern Africa, and the Kalahari in Namibia and Botswana in the southwestern part of the continent. Tropical rain forest prevails along most of the west coast, in the Zambezi valley of Mozambique, and in large areas of western equatorial Africa, including much of Gabon, Congo-Brazzaville, and northern Zaire. Forest, however, covers only about 10 percent of the land area. Rolling grassland, often called savanna or sudan, predominates between the desert-edge lands and the forest, both north and south of the equator. The desert and the equatorial forest have always been relatively sparsely populated; most Africans have always lived in coastal West Africa or the savanna areas north and south of the equatorial forest.

Paleontological studies indicate that hominids almost certainly evolved in Africa, and our species. Homo sapiens, probably was widely distributed over the continent by at least 40,000 years ago. Scattered bands of stone-age hunter-gatherers spread lightly over the entire continent. Signs of permanent settlement by fishermen around lakes and rivers are evident in eastern Africa and places that are now in the Sahara from about 7000 B. C. Knowledge of stockraising diffused from southwest Asia from about 5500 B. C., and agriculture followed the same course shortly afterward. The Sahara region did not begin to become a desert until about 2500 B. C., so these developments first reached peoples in and just south of the present Sahara. Here the new ways of life allowed the gradual development of settled village life, population growth, the rise of political and economic specialization, and, in general, the more complex societies associated with the Neolithic “Revolution.” Iron technology diffused from the North African coast to what is now the West African savanna by about 300 B. C., giving peoples in the belt south of the desert, the ancestors of most modern black Africans, an additional advantage over more isolated populations further south.

As of the first or second century B. C., demographic growth among these iron-age, agricultural groups was encouraging them to expand southward against weaker, less numerous hunting and gathering peoples. Peoples ancestral to the modern pygmies probably dominated much of the forest. Further south were the ancestors of the Khoisans, who once inhabited most of the southern third of Africa, but are now restricted to parts of the Kalahari and bordering regions. In the west the farming peoples soon reached a barrier, the Gulf of Guinea, but members of one linguistic group in the borderlands of modern Nigeria and Cameroun had a continent before them. For roughly 2,000 years these technologically superior peoples have been gradually colonizing half a continent, driving away, killing, or absorbing most of the indigenous groups. The descendants of these people, speakers of languages of the Bantu family, now dominate most of the continent from the equatorial forest almost to the southern tip.

Disease Patterns from A. D. 1000 to 1500

By about A. D. 1000, most of the better agricultural lands had been settled by village farmers. There was still a frontier in the extreme south, and pastoral groups were important in and near the deserts and in parts of the East African interior, but the pygmy and Khoisan peoples were increasingly being pushed into pockets of marginal jungle or desert - a process that has continued until the present. Farming was often of a slash-and-bum type, with villages moving to seek new lands at intervals of several years to a generation or more, but hundreds of people often lived close together in compact, relatively permanent settlements. Small cities began to develop in response to long-distance trade in parts of the western Sudan and along the east coast.

These long, complex processes must have had important implications for health conditions. Huntinggathering populations were too sparse to support many acute diseases, especially smallpox, measles, poliomyelitis, chickenpox, and other viral infections that produce long-lasting immunities. They were mobile enough to avoid living for long in close proximity to accumulations of their own wastes.

Village life, on the other hand, whether based on fishing and intensive collecting or on agriculture, put much larger numbers of people in close, continuous contact in fixed places. Diseases of crowds, like many of those caused by respiratory transmission of common bacterial and viral infections, could be readily transmitted. Disposal of wastes and contamination of water became problems, and failure to solve them resulted in much greater opportunities for the spread of gastrointestinal infections, such as dysentery and diarrhea of various etiologies, as well as Ascaris, Trichuris, and other parasitic worms. Hookworm, transmitted by fecal contamination of soil, was also common in many places. Villages and land cleared for agriculture helped provide breeding sites for the mosquito vectors of malaria, yellow fever, and filariasis. Animal husbandry also provided enhanced opportunities for transmission of beef and pork tapeworms, anthrax, and other diseases. Animal manure attracted disease-carrying flies. In Africa, as elsewhere, the price for the advantages of village life and a more reliable and abundant food supply was a dramatic increase in the variety and frequency of infectious diseases.

Africans gradually developed immunologic and cultural defenses against many of these diseases, and population grew, although much more slowly than in recent decades. Although direct evidence is lacking, it is likely that the pool of diseases afflicting sedentary populations was especially deadly for indigenous hunting-gathering groups beyond the expanding agricultural frontier. As in the Americas, Australia, New Zealand, and probably also Siberia, diseases from what William McNeill has called “civilized disease pools” helped to pave the way for newcomers by killing large numbers of the aboriginal populations.

By about A. D. 1000 the more densely inhabited portions of Africa, or at least those north of the equatorial forest, probably had had at least limited experience with most of the infectious diseases common to the Eurasian land mass. There was some attenuation, however, due to distance and relative isolation, as well as modifications from the tropical environment and the fairly low average population density. The disease mixture would be enriched and the frequency of outbreaks increased in later centuries as a result of more intensive commercial and other contacts with the Moslem world and with western Europe.

We have little direct knowledge of health conditions before about 1500, but scattered data and inferences from more recent times allow some general, if somewhat speculative, comments. Many Africans suffered from a wide range of intestinal parasites spread by the fecal-oral route, and from dysentery and other bacterial and viral diseases associated with poor sanitation, although cholera did not exist here until it was imported from Asia in the nineteenth century.

Some have argued that there is an old focus of plague in central Africa, but the evidence for this is not compelling, and it is not clear that plague had any real importance in Africa before the late nineteenth century. Smallpox was known in Egypt by the sixteenth century B. C., and may have been epidemic in Ethiopia as early as 570. South of the Sahara, smallpox and perhaps also measles were probably uncommon and tended to occur in epidemic form at long intervals. Respiratory infections like pneumonia were uncommon, and tuberculosis was rare or absent, except perhaps in trading towns. Cerebrospinal meningitis probably did not appear until the late nineteenth century. Guinea worm and schistosomiasis were, then as now, focal waterborne infections with high prevalence rates in some localities.

Except in the deserts, malaria was ubiquitous. It tended to spread in the forest as land clearance for farming created better breeding sites for Anopheles mosquito vectors. The antiquity of falciparum malaria is indicated by the widespread prevalence of sickle cell trait, a costly but effective genetic defense. Most African groups lack Duffy antigen, probably another old genetic adaptation, which protects them against vivax malaria. Yellow fever existed in forest areas, but attacked mainly children and may have caused relatively little harm. Yaws and leprosy were especially prevalent in moister climates. Trachoma was more common in arid regions. Gonorrhea probably had been established by the first century A. D., at least in the towns of the western Sudan, but syphilis was a post-Columbian import via Europe and North Africa. Human and animal trypanosomiasis occurred in places where tsetse flies lived. Then, as now, animal tr3rpanosomiasis prevented stock raising in forest areas. Pockets of savanna bush were infested with flies carrying both human and animal pathogens; these places were generally known and avoided.

Disease Patterns of 1500-1900

More intensive trade and political contacts with the outside world, especially Europe, developed from the sixteenth to mid-nineteenth centuries. These contacts, accompanied hy more extensive long-distance trade within Africa and by widespread patterns of political centralization, helped to spread many infectious diseases.

Europeans and Africans began a long commercial relationship with the arrival of the Portuguese in the fifteenth century. Trade grew rapidly over the centuries, and came to involve most of the states of western Europe and the Americas and, directly and indirectly, most African groups living within a few hundred miles of the sea. Coastal African merchants sold slaves, ivory, gold, dyewood, and other commodities for cloth, guns, metal goods, tobacco, alcoholic beverages, and other manufactured items. African products were obtained by trade networks extending far into the interior. Negotiations between the coastal middlemen and foreigners were often long and complex, providing ample opportunities for exchanges of pathogens; the trade routes provided paths for diseases to spread into the interior.

Among the most important and best documented diseases in early African history was smallpox. Although it was widespread in North Africa hy the seventh century, and had almost certainly reached the western Sudan as a by-product of the transSaharan caravan trade by about A. D. 1000, smallpox may not have been indigenous to the western coast or the southern half of the continent until the seventeenth century. Ships brought infection from abroad or carried it from place to place along the coast at irregular intervals, after enough time had passed to allow the appearance of a new generation of susceptibles. An epidemic caused great loss of life along the Gold Coast in the 1680s, and by at least 1700 some West African peoples had adopted or invented variolation techniques. Smallpox epidemics were frequent in the eighteenth and nineteenth centuries, and a major shipbome outbreak swept the whole coast as far south as Gabon and Angola in the early 1860s. In South Africa, where the Dutch East India Company had established a colony at Cape

Town in 1652, smallpox epidemics introduced by sea in 1713, 1755, and 1767 had serious demographic consequences for the colonists and were devastating for the indigenous and already hard-pressed Khoi pastoralists. On the east coast, it is likely that smallpox was an early accompaniment of the Indian Ocean trade, but there is little evidence for it in the pre-European period. The Portuguese recorded a major epidemic in 1589. Smallpox diffusion into the East African interior probably occurred later than in West Africa because of weaker trade networks; it may date back only to about 1800.

Measles and chickenpox were probably also introduced by traders from time to time, but there is little documentation. Tuberculosis probably reached coastal West Africa in the early days of contact, but it did not become widespread until after 1900. Venereal diseases were a different story; syphilis and gonorrhea were common among coastal groups by the eighteenth century, and these diseases must have spread inland as well. Gonorrhea may well have been an indigenous disease whose diffusion was facilitated by new conditions; syphilis almost certainly arrived from the outside world.

Trans-Saharan trade had existed for centuries prior to 1000, and no doubt the caravans, like the sailing ships, sometimes were accompanied by infectious diseases. Smallpox could well have reached the Sudanese market towns, either with infected merchants or in goods. Tuberculosis, measles, and gonorrhea no doubt diffused from North Africa with trade, although they may have already existed in the savanna. Similarly, the extensive pre-European trade along the east coast, between the Swahili towns and merchants from India, Persia, and Arabia, must have resulted in some disease transmission.

It is clear, despite the weakness of the data, that contacts with Europeans and other foreigners had serious disease consequences for many African peoples in the precolonial period, especially those along the west and east coasts and in the market centers for the Sudan. However, although some small groups may have suffered heavily, there was no postcontact pattern of mass death in Africa similar to what occurred in parts of the Americas or the Pacific. Africans shared enough of the Old World disease pool to avoid major demographic disaster. Stronger social systems of African peoples may also have played a role in their enduring and recovering from great epidemics. Even with the drain of the Atlantic, trans-Saharan, and Indian Ocean slave traders, Africa was not depopulated. Disease resistance, strong local social and political systems, and the introduction of new food crops like maize and manioc helped to sustain populations.

The African disease environment did have very serious consequences for foreigners. We still know relatively little about how Moslem traders fared, but North African visitors to the Sudan did try to finish their business before the rainy season brought malarial fevers, and Omani Arabs suffered severely from falciparum malaria on the Swahili coast.

The fate of Europeans on the west coast is much better documented. “Fevers” and “fluxes” - especially malaria, yellow fever, and the dysenteries - took a frightful toll among sailors, soldiers, traders, missionaries, explorers, and slavers. Studies of British, Dutch, and French experiences have shown that death rates of 50 percent in a year were not uncommon. It is possible that Portuguese death rates were somewhat lower, but they too paid a heavy price for their African commerce. Mortality prevented any serious European military activity in most of West Africa; maintaining weak, sickly garrisons in a few coastal forts was all that they could normally do. Disease not only helped save West Africans from European encroachment, but also gave them a considerable commercial advantage. African merchants could, and frequently did, drag out trade negotiations, knowing that the Europeans were anxious to complete a deal and leave before the fevers began to reduce their numbers. The limited Portuguese expansion in northern Angola, although hampered by disease, took place in a drier area where malaria was not as serious as elsewhere on the western coast. European colonization at the Cape was possible only because the Dutch were operating south of the tropical disease environment.

Africa was more important as a donor than as a recipient in the post-Columbian exchange of diseases. Falciparum malaria and yellow fever reached Europe from time to time, but probably did not have major demographic consequences there. Much more significant was the transfer of African diseases to the New World, mostly as a by-product of the slave trade. Falciparum malaria and yellow fever played a major role in the population history of the warmer parts of the Americas, from the southern United States to southern Brazil. Whites suffered severely, and these diseases were leading causes of deaths among the American Indians, especially in the Caribbean basin. The African hookworm, misnamed Necator americanus, came over in the bodies of enslaved Africans, and was a very serious cause of sickness and death in the southern United States and in much of the West Indies and Brazil well into the twentieth century. Other African diseases, including onchocerciasis, filariasis. Schistosoma man-soni infection, and yaws, also became established in American foci.

Cosmopolitan diseases like dysentery and smallpox were frequently introduced into ports along with cargoes of slaves. In Brazil, slave imports often rose when there was drought and famine in Angola. Drought conditions caused people to migrate in search of food; they tended to congregate, often as defenseless, disorganized refugees, in areas where they could find sustenance. Such aggregations encouraged flare-ups of endemic smallpox as well as the depredations of slavers. The virus was often transported by captives, and there is a strong correlation between smallpox epidemics in Brazil and in its Angolan slave supply territory.

In sum, the biological consequences of the African slave trade included millions of deaths in the Americas, among both Europeans and Indians. African labor was crucial in many New World economies, but the demographic costs were enormous for inhabitants of North and South America and for European sailors on slave ships, as well as for sub-Saharan Africa. Indeed, at least in the United States, the demographic balance was almost certainly unfavorable. About 300,000 Africans were imported, probably far fewer than the number of whites who died of falciparum malaria, yellow fever, and hookworm infection from the eighteenth to the early twentieth centuries. The period of the European conquest of Africa and the consolidation of colonial rule, roughly from 1880 to 1920, was the most deadly period in history for much of the continent. West Africa, perhaps because of its earlier experience with introduced epidemics, did not suffer as severely as portions of equatorial. East, and central Africa. Intensified long-distance trade, warfare, labor demands, and famine characterized this era, as many African peoples found their relative isolation shattered. People, pathogens, and vectors all moved, and there were radical changes in living conditions. Smallpox spread widely, especially in East Africa, where coastal Moslem merchant caravans had begun to operate in the interior from the 1830s. Cholera was introduced several times into East Africa and diffused over the trade routes, with an especially destructive epidemic occurring in the 1850s. Cerebrospinal meningitis epidemics appeared, probably for the first time, in the western Sudan in the 1880s; there were several great epidemics there and in parts of the Anglo-Eg3q)tian Sudan and East Africa during the twentieth century. On a less spectacular but still important level, even short-distance moves might bring people into contact with antigenically novel strains of familiar organisms, such as the protozoa that caused malaria and amebic dysentery.

Tuberculosis, noted in the coastal towns of West Africa around the turn of the century, spread slowly inland. In the Cape Verde Islands migrants returning from the United States facilitated the spread of infection by the 1880s. The rise of the mining industry in South Africa and the Rhodesias was dependent on migrant labor. Poor conditions in the mines in the early twentieth century led to extremely high tuberculosis rates and explosion of the disease among the rural African population as infected miners returned to their homes.

Besides mining, other development efforts of the colonial era often had unexpected and deleterious health consequences. Major infrastructure projects usually depended on migrant labor and sometimes took a heavy toll in lives. For example, thousands of workers conscripted in the savanna country of southern Chad and Ubangui-Chari died from dysentery, respiratory ailments, and other diseases during the construction of the Congo-Oc6an railroad in French Equatorial Africa in the 1920s. Water projects frequently facilitate disease transmission in tropical climates. The Gezira irrigation scheme in Sudan, for example, as well as the massive Volta Lake in Ghana, has resulted in hyperendemic schistosomiasis. On a smaller scale, dam ponds may also become foci for malaria and guinea worm infection, and, in parts of northern Ghana, dam spillways and bridge pilings provided breeding sites for the vector of onchocerciasis, a worm disease that often causes blindness.

Venereal diseases also diffused rapidly in the late nineteenth and early twentieth centuries, as labor migration and urbanization disrupted social patterns. Equatorial Africa experienced a very destructive gonorrhea epidemic as a direct result of harsh Belgian and French colonial policies; this resulted in widespread sterility, which is believed to be largely responsible for the very low fertility rates in the region even today. Movements associated with the early colonial period were also apparently responsible for great outbreaks of human trypanosomiasis in French Equatorial Africa and the Lake Victoria region of East Africa in the first decade of the 1900s. At least 250,000 died in East Africa alone.

On a more trivial but still significant level was the rapid spread of the burrowing flea Tunga penetrans (chigoes). This insect invades tissues under the nails and may result in secondary infections that cause disability, or a loss of digits or limbs. Native to Brazil, the fleas were introduced into the Senegambia region about 1800, and to the Angolan coast about 1850. From Angola they spread over central and East Africa in a few decades, causing great misery in any given place, until people learned how to remove them.

Disease Patterns of 1900-60

The most explosive and most destructive epidemic ever to strike Africa was the influenza pandemic of 1918-19. Introduced at Sierra Leone in late August 1918, and to ports around the continent in the next several weeks, the disease spread rapidly inland over the newly constructed colonial roads, railroads, and river transport systems. Diffusion was especially rapid on the southern African rail system and on the river steamers in the Belgian Congo. Indeed, so quickly did the disease move by these means, that places in the Congo only 100 miles from the coast were first attacked by way of the Union of South Africa. Almost every inhabited spot on the continent was struck in a matter of 6 or 7 months, graphic proof that the old isolation was gone forever and that the continent was an epidemiological unit closely linked to the rest of the world. Approximately 2 million people - about 2 percent of the population - died during the epidemic.

The demographic balance began to shift by the 1920s in much of West and South Africa, and by the 1930s elsewhere. The harsher aspects of colonial rule were being mitigated, famine relief was made more effective with better transportation, and medical measures began to have some effect. Progress was most rapid in the Belgian and British colonies and in French West Africa; medical services were slower to develop in Portuguese territories and in French Equatorial Africa.

Colonial medicine had little to offer Africans for many years, except for surgery, yaws therapy, and smallpox vaccination. But by the 1930s, efforts to control smallpox, cerebrospinal meningitis, tuberculosis, louse - and tick-bome relapsing fever, and other epidemic diseases were beginning to have some impact. Plague broke out in several territories in the early twentieth century, but public health measures prevented serious loss of life. Extensive efforts to contain tr5rpanosomiasis, primarily by vector control in the British colonies and by chemical treatment and prophylaxis in the French territories, had considerable success. The growing cities continued to function as nodes for the diffusion of infectious diseases into the countryside, but measures to improve water supplies and waste disposal, control malarial mosquitoes, provide vaccinations, and treat patients began to have a positive impact in almost all urban areas by 1940. Ironically, improved water supplies meant that fewer people were exposed to polio virus as small children when they were most likely to have mild or asymptomatic cases. Postponement of infection until adolescence created an increase in the number of paralytic cases in the postWorld War II period - an unintended by-product of incomplete sanitary reform.

The advent of sulfa drugs in the late 1930s and especially the antibiotics in the 1940s provided a revolution in the effectiveness and, consequently, the popularity of the colonial medical services. Africa’s rapid demographic growth dates from the late 1940s and is partially the result of the success of most colonial medical services in lowering death rates from bacterial diseases. Populations are growing at rates that will double the numbers of people in most countries in around 20 years, a situation that is already placing grave strains on medical services and food supplies.

Disease Patterns Since 1960

Most African states became independent after 1960, but they have not been able to effect radical improvements in health conditions. Colonial medical services and their successors in sovereign African countries have tended to stress therapy over prevention, and to favor cities over the rural areas. There has been some real progress. Smallpox has been eradicated, thanks to a concerted worldwide campaign. Vaccines, many developed only after 1960, have begun to make inroads against measles, diphtheria, polio, cerebrospinal meningitis, and other common infections, but new vaccines are urgently needed for other diseases, including malaria and the bacterial and viral agents of childhood diarrheas. The most urgent need is to improve rural water supplies and sanitation, which would greatly reduce the incidence of a host of infections. Greater attention to nutrition and to infant and child health is also essential.

Malaria and schistosomiasis are still major causes of morbidity and mortality, and almost no progress has been made against the common intestinal parasites. Even yaws, which is readily treated with penicillin, has reemerged in areas such as Ghana where economic distress has curtailed medical services. Similarly, internal strife and misgovemment in Uganda have disrupted tr3qjanosomiasis control, with predictable results. Campaigns sponsored by the World Health Organization and other groups against such major scourges as malaria, onchocerciasis, schistosomiasis, trypanosomiasis, and leprosy are promising, but high death rates, weak and sometimes declining economic and political systems, and the AIDS epidemic show that grave problems remain. More than ever, Africa’s disease environment is determined by its poverty.

K. David Patterson


Alden, Dauril, and Joseph C. Miller, 1987. Out of Africa: The slave trade and the transmission of smallpox to Brazil. Journal of Interdisciplinary History 18: 195-224.

Curtin, Philip D. 1968. Epidemiology and the slave trade.

Political Science Quarterly 88: 190—216.

Curtin, Philip D., et al. 1978. African history. Boston. Domergue-Cloarec, Danielle. 1986. Politique coloniale frangaise et rMites coloniales: La sante en Cote d’Ivoire, 1905-1958. Toulouse.

Ford, John. 1971. The role of the trypanosomiases in African ecology: A study of the tsetse fly problem. Oxford. Hartwig, Gerald W., and K. David Patterson. 1984. Schistosomiasis in twentieth century Africa: Historical studies in West Africa and Sudan. Los Angeles, eds. 1978. Disease in African history: An introductory survey and case studies. Durham, N. C.

Hoeppli, R. 1969. Parasitic diseases in Africa and the Western Hemisphere: Early documentation and transmission by the slave trade. Basel.

Hopkins, Donald R. 1983. Princes and peasants: Smallpox in history. Chicago.

Hughes, Charles C., and John M. Hunter. 1970. Disease and development in Africa. Social Science and Medicine 3: 443—93.

McNeill, William H. 1976. Plagues and peoples. Garden City, N. Y.

Patterson, K. David. 1979. Infectious diseases in twentieth-century Africa: A bibliography of their distribution and consequences. Waltham, Mass.

1981. Health in colonial Ghana: Disease, medicine, and socio-economic change, 1900-1955. Waltham, Mass. Patterson, K. David, and Gerald F. Pyle. 1983. The diffusion of influenza in sub-Saharan Africa during the 1918—1919 pandemic. Social Science and Medicine 17: 1299-1307.

Patterson, K. David, and Gerald W. Hartwig. 1984. Cerebrospinal meningitis in West Africa and Sudan in the twentieth century. Los Angeles.

Wiesenfeld, Stephen L. 1967. Sickle-cell trait in human biological and cultural evolution. Science 157: 1134-40.


Disease Ecologies of the Middle East and North Africa

This study of disease ecologies of the Middle East and North Africa aims to demonstrate the interrelationships of environmental and etiologic factors in the diseases endemic to that region. In so doing, the essay surveys the area between Morocco in the west and the Iranian border in the east, including the Anatolian Peninsula in the north and the Arabian Peninsula to the south.

Conditions before the mid-twentieth century are generally emphasized in this study. The population data and some obviously changing current conditions are, however, pertinent to conditions in the late twentieth century. The State of Israel is not included in the discussion because of the general time frame and for other reasons. Israel does not fit into most generalizations about the region because of its diversified economy and the comprehensive health-care system created by preindependence settlers. The chapter also will not deal with the region’s emerging pattern of the degenerative, metabolic, and genetic disease concerns of industrialized societies. Many of the data are derived from the accumulation of information assembled by the attempt of European nations to deal with epidemics and exotic diseases encountered during the nineteenth century in Africa and Asia. This material is sufficient to sketch a tentative disease profile, stressing infectious diseases. Moreover, twentieth-century investigations in nutrition have been used to supplement and qualify this information.

Geography, Topography, and Climate

The Middle East and North Africa occupy that part of the Earth’s crust where three tectonic plates converge, causing great ranges of high-fold mountains to be thrust up, notably in western North Africa and in the northern tier states of Turkey and Iran. Peaks in the high Atlas Mountains of Morocco and the Taurus range in Turkey exceed 12,000 feet, whereas Mount Damavand, in Iran’s Elburz mountains, exceeds 18,000 feet. Running north and south, the Hijaz, Asir, and Yemen ranges are high escarpments in the southwestern Arabian Peninsula, paralleling the anticlinal highlands that form the Lebanon and Anti-Lebanon mountains and the Judean Hills of Palestine.

The Middle East and North Africa lie roughly between latitudes 20° and 40° north in a transitional climatic zone between equatorial and mid-latitude climates. Because of general atmospheric circulation patterns, a characteristic of these latitudes is prevailing aridity - the “Mediterranean Rhythm” of winter rain and summer drought. Only westward-facing coasts and mountain ranges receive the 250 millimeters (about 10 inches) rainfall considered the minimum necessary for cultivation. The lack of cloud cover is a major factor influencing temperature, for clear skies and intense solar heating of the land cause very high temperatures during the day although temperatures fall considerably at night. Another characteristic of the region is scanty water supply. Except for the Nile, Tigris, and Euphrates, the majority of rivers are short streams with a rapid and intermittent course down rugged mountain sides. The lack of wooded land is another serious deficiency. Long occupation has meant prolonged exploitation of the land over millennia, almost total deforestation, and removal of ground cover, resulting in uncontrolled water runoff and soil erosion. Aggravated by overcultivation and unrestrained grazing, especially by goats, soil erosion has led to extensive desiccation and desertification. Hence, at mid-twentieth century, it was estimated that only 5 to 7 percent of the total area is cultivable naturally.

The implications of prevailing aridity and great expanses of mountainous or desert terrain have been significant for human survival: Population has been relatively sparse and discontinuous in distribution; until recently, nomadism was widespread; and settled argiculture most often has required irrigation and complex infrastructures to govern the allocation of scarce water resources.


The total population in 1984 of countries under consideration in the region, estimated at 257 million, was about 5.6 percent of the world population, in an area occupying about 10 percent of the Earth’s surface. The largest populations were in Eg3q)t, Turkey, and Iran, which comprised 52 percent of the inhabitants of the region.

Timkey was the only country in which population was distributed relatively evenly. Even at the midtwentieth century, about 75 percent of the inhabitants lived in small villages scattered over the Anatolian Peninsula, whereas in other states, the population had already been concentrated along the seacoast or river banks, on oases, or around the countries’ metropolitan centers. Since midcentury.

Population pressure on the land has reduced the percentage of people in agriculture and accelerated the move to urban centers. By 1984, it was estimated that 42 percent of the population of North Africa and 53 percent in the Middle East had gravitated to towns or cities. At the same time, 40 to 45 percent of the populations surveyed were under 15 years. (An overall annual growth rate of 2.8 percent means almost doubling the population in 25 years.)

About 93 percent of the people of the region are Muslim and about 57 percent speak Arabic; other important languages are Turkish, Persian, Hebrew, Kurdish, and Berber (Fisher 1971; Drysdale and Blake 1975).

Economic Life

Until very recently, about 60 percent of the population cultivated the traditional crops of the Mediterranean - cereals and olive and fig trees - whereas date palms and sugar cane predominated in the southern deserts. Antiquated and inequitable land-holding and tenancy systems have discouraged long-term development by individual farmers, and the traditional but excessive subdivision of land has worked against cost-effective production. This region still must remain vigilant for periodic swarms of destructive locusts, both Saharan and Arabian types, in addition to the pests that damage crops in other parts of the world.

Whereas most lands capable of cultivation have been planted with cereals, areas where water and good soil are lacking have been left to herders. Sheep are preponderant in all areas; goats also are kept in large numbers, especially in steppe and mountainous areas; and water buffalo have provided most animal power in the marshes of Iran and Iraq and the irrigated fields of Eg5q>t. As transport has become increasingly mechanized, the use of the camel has declined, but the donkey still carries people and commodities everywhere. Neither cattle nor horses are important economically because of lack of pasturage. Mineral resources are limited, with the exception of petroleum in some states, and large-scale extraction has begun only relatively recently. Good-quality coal exists only in northwestern Turkey, but hydroelectric power and petroleum have been supplying energy for industrialization in recent decades.

The traditional handicrafts and manufactures of the Middle East and North Africa - metal working, glassware, textiles for articles of clothing, and woolen carpet-making - have suffered from the competition of foreign imports, but many coimtries are now promoting them for export. Four countries-

Eg5q)t, Israel, Syria, and Turkey - no longer conform to the typical Third World economic pattern, in that one-fifth or more of their gross domestic product is derived from the manufacturing industry. Generally, however, the countries of the Middle East and North Africa belong to the Third World, being still heavily dependent upon the export of primary products and the import of food, consumer goods, equipment, and technology {Oxford Regional Economic Atlas 1964; Fisher 1971; Drysdale and Blake 1985).

Disease Patterns

The foregoing sketch suggests a distinctive ecological disease pattern for the Middle East and North Africa. Pastoralism and the farmers’ reliance on animals for transport, power, fertilizer, and dung fuel have made these occupational groups, living in close proximity to their livestock, vulnerable to zoonoses and to insect-bome diseases, some of which infest domestic or wild animals. Another important disease complex has developed out of the necessity for irrigation: the widespread incidence of parasitism due to favorable conditions for proliferation of the insect carrier and an intermediate host where required. At an agricultural conference in 1944, it was reported that expanding irrigation in one area of Egypt had raised the incidence of both malaria and schistosomiasis from 5 to 45 or even 75 percent of the population in that area (Fisher 1971). This survey, therefore, will begin with those ailments most closely related to the rural environment: arthropod-borne diseases and parasitic infestations. Next it shall consider the “crowd diseases,” most characteristic of urban societies, but also found in crowded villages and oases. Last it shall sketch the diseases caused by nutritional deficiencies among rural and city people. Within those categories, diseases are listed in descending order of their prevalence or importance as death - or disability-threatening experiences.

Major Arthropod-Borne Diseases Because the many species of anopheline mosquitoes have adapted to breeding in the widest variety of hydrological conditions - from swamps and stagnant irrigation pools to fast-moving mountain streams, and from freshwater springs to brackish mau-sh-land - they are foimd throughout the region except in stretches of desert lacking any surface collection of water. From 9 to 19 species of anopheline mosquitoes exist in each Middle Eastern and North African country, of which 3 or 4 have been identified as vectors of malaria.

Although mosquitoes cannot survive dry, hot

Weather, their proliferation in oases in Libya’s Fezzan Desert and in the Arabian Peninsula demonstrates their tenacity. One species of Anopheles endemic in southwestern Arabia has caused recurrent epidemics of malaria under favorable rainfall conditions. The last such epidemic was reported in 19501, when this species spread inland from Jidda along the road to Mecca, carried by the increased traffic of the Muslims’ annual pilgrimage.

Malaria has been reported in all the countries of the Middle East and North Africa. Since World War II the World Health Organization (WHO) has carried out extensive mosquito eradication projects. Nonetheless, malaria continues to break out periodically, and in 1950 a public health survey in Morocco reported that it was still the most prevalent disease in the country (Simmons et al. 1954; Nosologie maro-caine 1955; Ranter 1967; Benenson 1975).

The Aedes Aegypti mosquito that transmits dengue fever also is a potential vector of yellow fever, but that infection has not been reported in the Middle East and North Africa. Dengue is endemic in the eastern Mediterranean area but has not been observed at heights exceeding 600 meters (2,000 feet) and has been largely confined to coastal areas. Most countries in the Middle East have sporadic outbreaks of dengue fever, and a few cases are reported in Libya every year; whereas in Morocco, Algeria, and 'Tunisia, the infection has remained only a potential threat (Simmons et al. 1954; Ranter 1967; Benenson 1975).

Because early symptoms of Bancroftian filariasis may be simply fever and lymphadenitis, the disease was not reported historically until prolonged and repeated infection caused elephantiasis of the limbs or outer genitalia. Today, although the most common mosquito vector of filariasis is abundant throughout the region, the threat of the disease has remained potential. In Lebanon, filariasis appears occasionally. There is one focus of infection in the southwestern Arabian Peninsula and another in Egypt, where the mosquito vector proliferates in numerous brackish wells in Rosetta (Simmons et al. 1954; Benenson 1975).

Bubonic plague is transmitted by the bite of an infective flea, usually Xenopsylla cheopis, and marked by acute l5miphadenitis forming buboes, at the site of the infection; septicemic plague occurs in severe and advanced bubonic plague, causing petechial hemorrhages; pneumonic plague, the most infectious and fatal form, is airborne, spread by inhalation of exhaled droplets from infected patients.

The Middle East and North Africa suffered severely in the sixth-century plague of Justinian, and repeatedly thereafter. Because Procopius had placed the origin of that pandemic in Egypt, the Nile Valley became identified in Europe’s popular and professional imagination as “the cradle of plague.” However, the recurring epidemics of bubonic plague in this region were initially imported. Infected fleas on rats infesting the holds of cargo ships transmitted the infection to domestic rats in Mediterranean port cities and established endemic loci for the disease. Only the coast is naturally vulnerable to plague. Inland areas are too hot or too cold, and above all too dry to be susceptible to enzootic plague. However, irrigation systems acted as networks for transmitting infective fleas by providing harborage for rats in the embankments of canals. Epidemics flared periodically whenever optimum weather conditions - high humidity and moderate temperatures - coincided with an adequate rat-flea density. After the adoption of quarantine measures in the southern and eastern Mediterranean in the nineteenth century, followed by the discovery of the rat-flea nexus, most areas of the world including the Middle East and North Africa managed to bring plague under control until the epidemic of 1894, which originated in northern China.

Plague, however, continues to be a potential danger in the Middle East and North Africa. A reservoir of sylvatic (wild rodent) plague in the mountains of southwestern Arabia and the Rurdish highlands, shared by Iran, Iraq, and 'Turkey, may spread infection by contact with domestic rats. In Libya sporadic cases transmitted by steppe rodent fleas broke out almost annually from the time of World War I until 1940. In Morocco as well, plague recurred sporadically until 1946, and it was also reported in Tunisia, Algeria, and Egypt up to the early 1950s (Hirsch 1883; Hirst 1953; Pollitzer 1954; Simmons et al. 1954; Nosologie marocaine 1955; Ranter 1967; Benenson 1975; Gallagher 1983).

Characteristic of colder climates, typhus is not common in this region and has occurred chiefly during the winter among nomads who wear the same heavy clothing day and night. The human body’s humid microclimate provides a favorable environment for the louse to deposit eggs {nits) that hatch into young lice in a few days. Warm dry weather is unfavorable for breeding because humans dress more lightly, exposing the lice to high temperatures and sunlight. Displacement of people and crowding during World War II contributed to a series of epidemic outbreaks of typhus in North Africa, but delousing campaigns appeared to eliminate the disease. Nonetheless, occasional outbreaks have been reported in Iran, Iraq, S5T*ia, and Jordan, from congested villages and town quarters as well as from refugee camps (Rodenwaldt 1952; Simmons et al. 1954; Nosologic marocaine 1955; Ranter 1967; Benenson 1975).

Other Arthropod-Borne Diseases

Although foci for endemic tick-borne relapsing fever (alternating febrile and afebrile periods) exist throughout the region, the disease is rare. Epidemic louse-borne relapsing fever is more common; between 1942 and 1945 a series of epidemics spread throughout North Africa from Morocco through Eg5q)t and extended into Turkey, but it has occurred only sporadically since then. Boutonneuse fever is a mild to moderately severe febrile illness widely distributed in countries adjacent to the Mediterranean, Caspian, and Black seas. The disease, which is transmitted by the bite of an infected dog tick, occurs occasionally in Morocco, Algeria, Tunisia, Libya, and Turkey, and rarely in Israel and Lebanon. Also, another tick-borne disease, tularemia, a plaguelike infection of wild and domestic animals, especially rodents and rabbits, is found only in Turkey (Rodenwaldt 1952; Simmons et al. 1954; Benenson 1975).

Of the three types of leishmaniasis, only cutaneous leishmaniasis {Leishmania tropica) is common in the Middle East and North Africa. In 1756 Patrick Russell named the affliction the “Aleppo boil,” and today it is also known as “Baghdad boil” in Iraq and “Jericho boil” in Jordan. In Israel it is most common in the Haifa area. It also occurs sporadically in the Arabian Peninsula and in southeastern Turkey, where it is known as “Urfa sore.” In North Africa cutaneous leishmaniasis is endemic and prevalent in Algeria and Morocco, widespread in Tunisia and Eg5q)t, but rare in Libya (Russell 1794; Rodenwaldt 1952; Omran 1961; Ranter 1967; Benenson 1975).

Kala-azar, or visceral leishmaniasis, is a chronic systemic infection disease characterized by fever, enlargement of the liver and spleen, anemia, and progressive emaciation and weakness. Untreated, it is a highly fatal disease. Although the vectors of kala-azar are not common in this region, three species of sandflies are suspected of transmitting visceral leishmaniasis that appears sporadically in the northern and western coastal provinces of Turkey, and the littoral of Algeria and Morocco (Simmons et al. 1954; Benenson 1975).

Sandfly fever or pappataci fever (phlebotomus fever) is a viral 3- or 4-day fever that resembles influenza and is carried by the same phlebotome - Phlebotomus papatasii - transmits cutaneous leishmaniasis. Sandfly fever reportedly is endemic in Syria, Lebanon, Israel, Iraq, Iran, and sporadic in Jordan and Saudi Arabia (Simmons et al. 1954; Benenson 1975).

Finally, numerous species of flies are abundant throughout the Middle East and North Africa; among the most common of these are species of the Muscidae family, thought to be implicated in the mechanical transmission of intestinal and eye infections. For example, gastroenteritis causing infantile diarrhea and dehydration, which has been held responsible for more than half the infant deaths in Egypt, shows a striking peak of incidence during the hot, dry, fly season (Labib 1971). Several species cause myiasis in livestock and occasionally in humans, but cases of these invasions are rare (Simmons et al. 1954).

Helminth-Transmitted Diseases Of the four species of blood flukes infecting humans — Sc/iistosoma haematobium. Schistosoma mansoni. Schistosoma intercalatum, and Schistosoma japonicum - only the first two are endemic in the Middle East and North Africa. Persistence of the disease depends upon the presence of freshwater snails as the intermediate hosts.

The evolution of schistosomiasis probably occurred during the period when human populations were shifting from hunter-gathering economies to societies based on settled agriculture. Parasitism requires a stable relationship between host and parasite, such as is available in settlements close to slow-moving water in which snail hosts of the disease dwell. Vesical or urinary schistosomiasis probably existed in both ancient Mesopotamia and Egypt. Babylonian inscriptions and Egyptian pa-p)Ti (Ebers, Rahun) refer to hematuria and prescribe remedies. In 1910 Marc Ruffer discovered ova in Egyptian mummies dating from 1200 B. C., and J. V. Rinnear-Wilson considers the finding of shells of the most common host snail, Bulinus truncatus, in the mud brick walls of Babylon evidence that S. haematobium was the cause of hematuria described in Babylonian texts. French soldiers suffered with hematuria during the occupation of Egypt in 1798-1801, but the causative parasite was not identified until 1851 when Theodor Bilharz recovered adult worms from the portal system during an autopsy in Cairo. The life cycles of the intermediate molluscan hosts were demonstrated early in the twentieth century.

Studies and clinical records between 1931 and 1961 reported schistosomiasis in all the countries of the Middle East and North Africa. However, because of prevailing desert conditions, North Africa, except for Egypt, has not harbored parasites that require surface water or moist soil for survival. A notable exception is the Fezzan in Libya, where in some oases with shallow wells, up to 86 percent of the inhabitants have been infected. However, outside a relatively small radius the groundwater available to oases has too high a salt content to support the host snail. The highest incidence, up to 100 percent in some villages, has occurred in Iraq and especially in Egypt where the inhabitants of the Nile Valley have maintained irrigation systems for millennia.

The widespread species has been S. haematobium; infection with S. mansoni has appeared only in Egypt and among Yemeni and Iraqi immigrants to Israel, although the host snail exists in the Arabian Peninsula and North Africa (Ruffer 1910; Simmons et al. 1954; Nosologie marocaine 1955; Malek 1961; Farooq 1964; Ranter 1967; Kinnear-Wilson 1967; Benenson 1975; Sandbach 1976; Sandison 1980).

Ancylostomiasis, or hookworm disease, is probably quite old. A chronic disease of the digestive system described in the Ebers Pap3Tus of 1550 B. C. has been interpreted as hookworm disease. In 1838 Angelo Dubini discovered a worm that he called Ancy-lostoma duodenale, during autopsies in Eg5qjt, and a colleague found the same parasite during autopsies in 1845, but neither related them to specific diseases. In 1853, Wilhelm Griesinger identified ancylostomiasis as the cause of the endemic anemia, called “Eg3q)tian chlorosis,” and observed that 25 percent of the causes of death were traceable to the effects of this infestation.

Ancylostomiasis occurs in all Mediterranean countries, but the Nile Valley has been a particular locus of the infection (Khalil 1932; Simmons et al. 1954; Nosologie marocaine 1955; Benenson 1975).

Ascariasis (infection of the small intestine caused by Ascaris lumbricoides, the large intestinal roundworm) may cause digestive and nutritional disturbances. Pictorial evidence demonstrates the presence of Ascaris in ancient Mesopotamia, and numerous prescriptions for roundworm in the Ebers Papyrus indicate that the ancient Egyptians complained of this parasite as well. In the twentieth century, ascariasis has been most common among school children, who may suffer anemia and eosinophilia from high infestation. Serious complications among children may include bowel obstruction and occasionally death due to the migration of adult worms into liver or gallbladder (Simmons et al. 1954; Ranter 1967; Kinnear-Wilson 1967; Benenson 1975; Sandison


Other worm-related diseases include trichinosis, which, because of the Muslim and Jewish prohibition against pork, is rare in the Middle East and North Africa, and has been reported only in Lebanon. Taeniasis, an infection with the beef tapeworm. Taenia saginata - causing anorexia, digestive disturbances, abdominal pain, and insomnia - occurs where the larvae are ingested with raw beef. It is particularly frequent among herding peoples whose sheep, cattle, and dogs have a high rate of infection, which may be passed to humans. In Libya, for example, the government hospital at Benghazi reported the existence of the larval form of tapeworm in 20 to 28 percent of the patients annually between 1960 and 1963 (Ranter 1967; Benenson 1975).


The zoonoses that occur in the Middle East - brucellosis, anthrax, and Q fever - are all occupational diseases of herders, farm workers, veterinarians, abattoir workers, and industrial workers who process hides, wool, or other animal products. Brucellosis, which causes a generalized infection, also known as undulant fever, has been reported in Morocco, Algeria, Tunisia, Iran, Turkey, Syria, and Lebanon. Anthrax, an infectious disease of ruminants, occurs only in Turkey. Q fever rarely infects humans in areas where the disease exists enzo-otically in animals. Occasional cases, however, have been reported in Morocco that were suspected of having been transmitted by tick vectors.

Also increasingly rare is rabies or hydrophobia, an acute, almost invariably fatal viral infection of the central nervous system, transmitted to humans by the bite of a rabid animal. At mid-twentieth century, James Simmons and colleagues (1954) reported rabies in Iran, Syria, and Jordan; however, most countries in this region have controlled rabies by quarantining and licensing pets and by destroying stray animals (Benenson 1975).

Food - and Waterborne Enteric Diseases Acute diarrheal disease in early childhood, most prevalent after weaning, is important in the Middle East and North Africa as in all developing countries. Although it may include specific infections, infantile diarrhea frequently is a clinical syndrome of unidentifiable etiology caused by bacteria, viruses, helminths, or protozoa. Common in areas of poor sanitation and prevailing malnutrition, infant diarrhea May produce as many as 275 attacks per 100 children per year, more than 50 deaths per 1,000 per year in preschool children. Protein—calorie malnutrition is commonly associated with acute diarrheal episodes, which may precipitate kwashiorkor. The highest incidence tends to occur in hot, dry periods, calling for oral rehydration therapy, which has become a high priority program for the WHO in recent years (Simmons et al. 1954; Benenson 1975).

At mid-twentieth century, Simmons reported “dysenteries” for all Middle Eastern countries, but provided no data. All North African countries, including Egypt, reported higher incidence rates for shigellosis then amebiasis, except in Morocco and Libya, where amebiasis was reported more prevalent. Between 1900 and 1950 comparative mortality rates were 8.7 percent for amebic dysentery and 11.8 percent for bacillary dysentery (Rodenwaldt 1952; Simmons et al. 1954; Kanter 1967).

In the Middle East and North Africa, raw fruits and vegetables handled by infected persons are important vehicles of the transmission of typhoid fever, and flies are often vectors for spreading contamination. At mid-twentieth century, the disease was reported in all countries considered in this survey but was reported as rare in Libya (Rodenwaldt 1952; Simmons et al. 1954). Paratyphoid infection due to Salmonella of all groups except S. typhosa is a generalized bacterial enteric infection, clinically similar to but with a lower fatality rate than typhoid fever; it occurs only sporadically in this region.

Cholera did not appear in the Middle East and North Africa until the great pandemics of the nineteenth century that were caused by troop movements in the lands bordering India, Afghanistan, and Iran, and by accelerated sea transport linking Asia with the rest of the world. Six pandemic waves of cholera swept around the world between 1817 and 1923, invading all settled communities in Asia, Africa, Europe, and the Americas. Middle Eastern and North African countries were vulnerable to invasion by the disease because returning Muslim pilgrims carried the infection from the holy cities of Arabia, where it was introduced by Muslims from South Asia. After discovery of the cholera vibrio and the rationalization of quarantine practices, as well as nineteenth-century sanitary reform programs, cholera receded as a major threat. The adoption of efficient control techniques, particularly since the Second World War, has effectively neutralized the danger of dissemination from the Muslim pilgrimage sites. The last major outbreak, which occurred in Egypt in 1947, was due to relaxation of quarantine regulations during the Second World War. However, since 1961 a new strain of cholera, El Tor, has spread extensively from a focus in Sulawesi in Indonesia, through most of Asia and the Middle East into Eastern Europe and Africa, and from North Africa into the Iberian Peninsula and Italy (Hirsch 1883; Simmons et al. 1954; Pollitzer 1959; Kanter 1967; Benenson 1975).

Diseases Transmitted Through the Respiratory Tract

Tuberculosis is widespread in the Middle East in the pulmonary form that was known earlier as phthisis or consumption. Egyptian wall paintings depict humpbacks typical of bone tuberculosis of the spine, known as Pott’s disease, and tuberculous bones have been found in tombs dating to 3000 B. C. In modern times, tuberculosis appeared to accompany the rise of industrialization and urbanization in the nineteenth century, succeeding smallpox as the most common affliction in city life. In congested slums tuberculosis assumed epidemic proportions because the infection is transmitted by exposure to the bacilli in airborne droplet nuclei from the sputum of infected persons. In the mid-twentieth century, tuberculosis was reported in all Middle Eastern and North African states. Wartime displacement had caused a steep rise in incidence. In Libya, for example, many uprooted nomads from the Fezzan emigrated to shanty towns on the coast. Because food was scarce and sanitary installations were nonexistent, tuberculosis spread rapidly among these desert people in a severe form that was often fatal. In the 1950s, the WHO and UNICEF supported immunization programs with the result that tuberculosis in the Middle East has become similar to the European type, milder and chronic (Simmons et al. 1954; Nosologie marocaine 1955; Kanter 1967; Benenson 1975; Sandison 1980).

By contrast, pneuomococcal pneumonia was reported to have a significant mid-twentieth-century incidence only in Egypt and Turkey. This may suggest susceptibility among the ill-housed, undernourished poor inhabiting the overcrowded metropolises, as well as an above-average involvement among the coal miners in Turkey (Simmons et al. 1954; Benenson 1975).