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Humanitarian crises, population displacement and epidemic diseases, 1901–2010

Humanitarian crises, population displacement and epidemic diseases, 1901–2010

Cholera in Haiti

Wars, political upheavals, environmental disasters and other forms of humanitarian crisis have served to precipitate the mass displacement of populations since biblical times. Historically, large-scale population upheavals have resulted in disruption of livelihoods, social support mechanisms and health care delivery. The dislocation of food production systems has frequently led to chronic malnutrition and an increased susceptibility to infectious diseases, while the intensive mixing of populations in relief camps or other makeshift forms of shelter, often with poor levels of hygiene and under conditions of stress and malnutrition, have added further to the disease risks of displacement. Sexual violence and exploitation, especially of refugee women, have raised the spectre of HIV/AIDS and other sexually transmitted infections, while environmental changes and/or exposure to new environments have promoted the processes of disease emergence and re-emergence.

This project examines the mass population displacement–disease link attributable to the nexus of causes – including war, political repression, development projects, environmental change and disasters. The overarching aim is to produce the first systematic study of the global geography of epidemic-prone infectious diseases associated with mass population displacements in the twentieth and early twenty-first centuries. The focus is upon understanding the geographical patterns (most forced population displacements are geographically local; Figure 1), processes, and the demographic and health consequences of the population displacement. The project is permitting the creation, for the first time, of a standard and comparative profile of all mass movements of displaced persons, the infectious diseases entrained and their impact including the size of the population affected, duration of the event, mortality and morbidity rates, estimates of the years of potential life lost, and measures of the immediate and long-term health, demographic and economic consequences of the displacement event.

The project could scarcely be more timely. The Arab Spring resulted in the geographical displacement of many hundreds of thousands of people over the last 18 months. In 2013 alone, the Syrian uprising produced over 150,000 refugees in Turkey, Lebanon, Jordan and Iraq. Environmental disasters, too, have added to the recent mix of displaced persons. The Japanese tsunami of 2011 makes the point, with some 500,000 having been displaced by the triple disaster of earthquake, flood and nuclear accident. All these events have had disease-related consequences for the displaced populations and, in some instances, for the populations into which they have fled.

The epidemic-prone diseases that are most commonly entrained with displacement events include cholera (Figure 2), dysentery, typhoid fever and other diarrhoeal diseases associated with contaminated water supplies and insanitary living conditions. Crowd diseases such as measles have been documented as leading causes of mortality in the relief camps of Africa, Asia and Central America, while the movement of displaced populations to and through areas of endemic malaria has occasionally resulted in high malaria mortality rates in Africa and Asia. Asia and Africa have also witnessed the epidemic spread of meningococcal meningitis among refugee populations while, in Africa at least, significant outbreaks of hepatitis E have also been recorded. On occasion, other diseases have had a severe impact on the displaced. Prominent examples from the last 50 years include smallpox among Bangladeshi returnees from India, louse-borne typhus among the internally displaced in Burundi, visceral leishmaniasis among the internally displaced in Sudan, schistosomiasis among Cambodian refugees in Thailand and scrub typhus among refugees on the Thai-Burmese border.

Figure 1. Origin and destination of refugee flows, 1962–2010. For each WHO region, the circle maps show the percentage of the total refugee outflow from each country which went to contiguous countries (blur circle segments). Countries which shared a length of common border were defined as contiguous.

Figure 1

Figure 2. Cholera in Haiti. The biggest cholera outbreak since the middle of the nineteenth century occurred in Haiti from 2010 among the people displaced by a devastating earthquake. The illustrations show a makeshift camp and rehydration of cholera victims in a field hospital.

Figure 2