The prevalence of infectious diseases in a country has a striking impact on the likelihood of civil war, according to research by Matteo Cervellati, Uwe Sunde and Simona Valmori, published in the December 2017 issue of the Economic Journal.
Their study combines databases on epidemiology and civil wars from around the world over the past 50 years to provide evidence for the importance of disease as a factor in outbreaks of conflict. At a time when global warming is expanding the habitat for the vectors of many diseases, this is a significant addition to other influential factors such as ethnic tensions, control over natural resources and political power.
What''s more, to the extent that civil violence constitutes one of the major impediments for economic development, these findings also suggest that health interventions might have important secondary implications.
Since the end of the Second World War, civil wars have been responsible for a higher death toll than conflicts between countries or any other type of conflict. In addition to conflict-related casualties, civil wars typically lead to increased disease-related fatalities by disrupting infrastructure, prohibiting access to health services and facilitating the spread of infections and epidemics.
But what about the potential of a causal relationship in the opposite direction: from the disease environment to civil conflicts? Until now, this has been little studied and understood.
Yet poor health conditions may have a crucial influence on the costs and incentives an individual faces in considering whether to engage in civil violence. People with poorer health and higher exposure to potentially fatal infections that are outside their control are likely to be more willing to take risks, discount the future more – and become more vulnerable to violent attacks.
By investigating whether variation in health threats and the outbreak of epidemics can have an impact on the outbreak of civil violence, this study takes a fresh look at the subject.
The analysis builds on civil conflict data from across the globe at an annual resolution, covering the past half-century. These data are combined with information from epidemiological databases measuring exposure to infectious diseases. This approach makes it possible to uncover the causal relationship between disease exposure and outbreaks of civil conflict within a country, rather than the other way round.
In a first step, the analysis establishes a link between the disease environment and the frequency of outbreaks of civil conflict. To rule out effects from conflict to disease prevalence, the identification strategy focuses on the exposure to a particular class of diseases that are essentially non-eradicable and non-preventable, and which cannot be communicated or spread through conflict.
These ''multi-host vector transmitted diseases'' – examples of which include dengue fever – cannot be transmitted human-to-human. Instead, transmission requires a vector, typically an insect such as a mosquito in the case of dengue. In areas where such a disease is not present since the environment is not suitable for the vector, the disease is not introduced as a consequence of civil conflict or conflict-related population movements.
In a second step, the analysis considers variation in weather conditions as a potential trigger of health shocks. The background for this is that variation in weather can be exploited to investigate the impact of variation in the effective exposure to disease on civil conflicts due to its effects on the transmission vectors. The findings show that weather extremes have a different impact in terms of the outbreak of civil conflict if they happen in an area with few or many multi-host vector transmitted diseases.
The results document that disease prevalence is strongly linked to conflict incidence and that weather variation crucially influences this link, providing evidence for the importance of disease as a factor in outbreaks of civil conflict.
This evidence for a relevant role of the disease environment and the related risk of epidemics for civil violence sheds new light on the determinants of civil war, above and beyond factors such as ethnic tensions, control over natural resources and political power that have been documented in previous research.
A prime implication of this research is that the importance of disease as a factor in outbreaks of civil conflict deserves greater awareness, in particular as global warming is expanding the habitat for the vectors of many diseases. To the extent that civil violence constitutes one of the major impediments for economic development, this evidence also suggests that health interventions might have important secondary implications.
''Pathogens, Weather Shocks, and Civil Conflicts'' by Matteo Cervellati, Uwe Sunde and Simona Valmori is published in the December 2017 issue of the Economic Journal. Matteo Cervellati and Simona Valmori are at the University of Bologna. Uwe Sunde is at the University of Munich.