They're probably the most important diseases you've never heard of -- causing everything from greusome limb disfigurement and skin sores to bladder and liver cancers to neurological damage -- and they're practically ubiquitous among world's poorest people. Typically, such infections last for years or even decades, causing chronic and permanent disabilities such as stunted growth and intellectual developments in children; blindness, heart disease, and disfigurement of adults; and pregnancy complications that can result in severe disease in both newborns and their mothers. In so doing, neglected tropical diseases (NTDs) have been shown to acutally cause poverty and even destabilize communities, leading to conflict.
Because they strike mostly forgotten people living on less than $2 per day, NTDs have traditionally been thought of as a problem exclusive to low-income countries, especially in sub-Saharan Africa (where indeed they are important public health threats). But our latest research shows that most cases of the worst NTDs (defined by disability-adjusted life years lost) actually occur among the extreme poor who live in the large emerging market economies that comprise the G-20, together with Nigeria, which has a GDP equivalent to several Western European countries (See Table).
For example, more than two-thirds of the reported cases of visceral leishmaniasis, which causes a leukemia-like chronic illness, are found in G-20 countries, led by India, Brazil, China, and Italy. Similarly, 60 percent of those who require treatment for lymphatic filariasis, responsible for elephantiasis, live in India, Indonesia, Nigeria, and Brazil; while more than 70 percent of food-borne trematode infections, which cause liver cancer and severe lung disease, are found in China, South Korea, and Russia. Almost two-thirds of the global cases of Chagas disease -- which causes cardiomyopathy and other life-threatening heart diseases -- are in Brazil, Argentina, Mexico, and the United States, and 77 pecent of the world's leprosy cases occur in G-20 countries, led by India, Indonesia, Brazil, and China. Together, the G-20 countries and Nigeria also account for almost half of the world's cases of hookworm infection, while a large number of schistosomiasis cases -- responsible for chronic renal disease, female genital ulcers, and liver disease -- are in Nigeria, South Africa, Brazil, China, and Saudi Arabia.
Much of the disease burden within G-20 countries falls on the poor in Indonesia and the BRICS (Brazil, Russia, India, China, and South Africa), but there are also several serious NTDs found in Eastern and Southern Europe, and in the southern United States, including Chagas disease (heart disease), cysticercosis (seizures and other neuologic illness), and dengue (breakbone fever). New U.S. poverty statistics indicate that today almost 1.5 million American families surive on $2 or less in income per person per day in any given month. Many of the poorest -- and most disease-prone Americans -- reside in Texas and other parts of the Gulf Coast region.
Other locations within the G-20 that are particularly hard hit include areas of extreme poverty in southern Mexico, Saudi Arabia, and the northern territories of Australia (which is heavily populated by aboriginal populations) (See Figure). Instead of thinking of global health in terms of "developing" and "developed," therefore, it makes more sense to conceptualize NTDs as pockets of disease endemicity in areas of intense poverty throughout the world. These pockets occur, of course, in sub-Saharan African and other low-income regions, but they also afflict the world's wealthiest and largest-GDP countries -- countries with enormous financial and scientific capacity to combat and eliminate NTDs.