Human, crop, and animal diseases may trap this African farmer in poverty.

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Why so much of the world is stuck in a ‘poverty trap’

In a tiny village just a few kilometers outside of Dakar, farmers struggle to get by on the equivalent of $2 a day. They live off the milk of their cows, sell the wool of their sheep at local markets, and put their children to work tending the fields. Yet none of this is enough to raise them out of poverty. It’s like filling a leaking bucket with water: No matter how much effort they put in, they never succeed in making enough to meet their daily needs.

Now, for the first time, scientists have found a way to determine the root causes of this “poverty trap”: Disease, whether of humans, animals, or crops, tends to rob the world’s poorest people of their livelihood, keeping them destitute regardless of how hard they work or how much economic aid they get. But the study also suggests possible solutions.

The work provides important insights and implications for future interventions, says Chris Desmond, an expert on social development at the Human Sciences Research Council in Dalbridge, South Africa, who was not involved in the research. “Policymakers need to look at the public health situation, the access to primary health care, the condition of biological pests in the environment,” he says. “They need to look at all those things before they can decide what type of intervention to do.”

To conduct the research, scientists led by Calistus Ngonghala, a mathematician at the University of Florida in Gainesville, collected both economic and disease data from 83 of the most and least developed countries. The data included annual income per person and the impact of diseases in terms of financial cost, disease incidence, and mortality, which vary dramatically around the world. For example, the caterpillar of the armyworm moth destroys crops in places like Brazil and Zimbabwe, but can’t survive in places with temperate climates like Romania. Similarly, human diseases like malaria and dengue fever abound in places like Kenya and Cambodia, where the tropical climate favors their spread, and these countries also happen to offer limited access to health care. The researchers used these and related data to “train” mathematical models to determine how economic and disease factors, as well as ecological factors such as the growth rate of fish populations and other natural resources, affected poverty.

The models show that poor people who live in areas with limited human, animal, and crop disease might be able to lift themselves out of poverty either through their own means or with a bit of economic assistance, such as money to buy more crops and cattle. But in places of high disease and limited means of combating it, people could be stuck in poverty, no matter how much economic aid they receive, the team reports this month in Nature Ecology & Evolution.

“If you’re a subsistence farmer, infectious diseases not only affect your health, they also affect your earning, because you depend on your physical labor to get an income,” Ngonghala says. “We were surprised when we realized that in some instances economic aid is not going to help at all.”

Considering that more than 10% of the world, or about 800 million people—live in extreme poverty, the study suggests that most of them will never escape it unless issues beyond mere income are addressed.

One effective way to break poverty traps may be structural changes such as increasing access to health care by reducing health care costs, and preventing disease transmission through vaccine coverage. Once people are able to get well and safeguard their crops and livestock, they also might be able to dig themselves out of poverty, says study co-author Matthew Bonds, an economist at Harvard University.

Bonds uses as an example Rwanda, a sub-Saharan country that succeeded in reducing extreme poverty and hunger as part of the Millennium Development Goals, a series of international development goals for the year 2015. “[Rwanda] has had a major investment in health infrastructure and health systems,” he says. “Most people can get access to health insurance and to most forms of health care inexpensively.” In addition, foreign businesses are investing in the country’s energy and telecommunication sectors, helping to lift people out of poverty traps, he says.

However, the study can’t tell whether additional health interventions in Rwanda would result in more economic growth. To address that, the researchers would need a detailed survey of the country’s pests, epidemics, and per person income. “Our models simply show theoretical possibilities, they do not provide conclusive evidence,” Bonds says. Yet, he adds, the models predicted health interventions to be the most significant drivers of positive economic outcomes. “You can’t lose with health care.”