I teach molecular biology at the Universidad Nacional Agraria La Molina, in Lima, and every semester I open the course with the same exercise. I ask the room to name a drug that exists because someone funded tropical disease research. Artemisinin for malaria, someone says. Benznidazole for Chagas, says another. The antimonials for leishmaniasis. Then I put the dates on the board: artemisinin was first isolated in 1972; benznidazole was registered in the 1970s; the pentavalent antimonials date to the 1940s. The newest drug on that list is older than most of my students’ parents. Then I ask the question this article answers: why?
The short answer has a name: the 10/90 gap — the mismatch between where the world’s illness sits and where its research money goes. Roughly 90% of avoidable death and disability is concentrated in low- and middle-income countries, yet for decades only about 10% of global health research funding was aimed at the diseases that dominate those countries. The exact figures move from year to year, and I will show you the modern accounting below, but the pattern has held since the 1990s. From a lab bench in Peru, it explains almost everything about which tools I have and which I do not.
What Is the 10/90 Gap?
The phrase comes from the Global Forum for Health Research, a Geneva-based body that in the late 1990s began tallying who spends what on whose diseases, building on a 1990 report by the Commission on Health Research for Development. Its headline was blunt: about 10% of the world’s biomedical research dollars were addressing the health problems responsible for about 90% of the global burden of disease.
Today the accounting is done in more detail. The G-FINDER report, produced annually since 2008 by the group Policy Cures Research, tracks research and development — R&D, the money that turns a molecule into a medicine — for what the World Health Organization calls neglected tropical diseases, or NTDs: a list of roughly twenty poverty-linked illnesses that includes Chagas disease, leishmaniasis, dengue, chikungunya and the parasitic worms. The WHO estimates that more than one billion people carry at least one of them.
By G-FINDER’s recent counts, the whole world spends somewhere around US$4 billion a year on neglected-disease R&D. That sounds like a lot until you set it beside total pharmaceutical R&D spending, which runs well past US$200 billion a year. All neglected diseases combined receive under 2% of it. The classic citation here is a study by Trouiller and colleagues in The Lancet (2002): of 1,393 new medicines brought to market between 1975 and 1999, sixteen — about 1% — targeted tropical diseases or tuberculosis.
One more number, because it is the unit the big institutions think in. A disability-adjusted life year, or DALY, is one year of healthy life lost, whether to early death or to disability. Funding bodies rank projects by cost per DALY averted. The trouble is that the diseases with the least data produce the least precise DALY estimates, and the least precise estimates are the easiest to rank low. Underfunding generates undercounting, which justifies underfunding. The gap defends itself.
Why the Money Does Not Follow the Sickness
Here is where I use my favorite Lima analogy. A combi does not run a route because people along it need transportation. It runs because passengers pay the fare. If a hillside needs service but nobody can pay, no route appears, no matter how real the need. Pharmaceutical research is a route map drawn the same way: companies invest where the fares — the expected returns — are. A new psoriasis biologic has paying passengers for decades. A new Chagas drug would mostly serve people earning a few dollars a day, in countries whose health budgets are counted in hundreds of millions, not billions.
Developing a single new medicine is estimated to cost between several hundred million and more than a billion dollars, and to take a decade or longer. A company answering to shareholders cannot rationally spend that on a product that cannot pay it back. This is a market failure, not malice — the market is doing exactly what markets do. The result is that the diseases of the poor keep getting the drugs of the past.
Two structural details make it worse. Patents run twenty years from filing, and clinical trials eat most of that clock, so slow, chronic diseases like Chagas — which can take decades from infection to heart failure — make weak business cases even where a market exists. And the big regulators that set global standards, the FDA and the EMA, sit in countries with almost no patients for these diseases, so trial designs and even definitions of success are built elsewhere. The samples fly north; the questions fly with them.
What the Gap Looks Like from a Peruvian Bench
Come down to bench level with me. In the Peruvian Andes, cutaneous leishmaniasis is called uta — the Quechua name that appears in colonial chronicles centuries before anyone had seen a parasite. In the Amazon lowlands, the same parasites can cause the mucocutaneous form, espundia, which erodes nose and palate. Peru registers several thousand cases in a typical year, and the count swings more with surveillance effort than with any real change in transmission.
Our first-line drugs are still the pentavalent antimonials — antimony-based compounds developed in the 1940s, given by injection for about twenty days, with enough pancreatic and cardiac toxicity that we check blood enzymes and heart traces during every course. The only oral option, miltefosine, was registered in some neighboring countries years ago but remains hard to find in Peruvian pharmacies. Adherence matters for a mechanism reason: killing intracellular parasites is enzyme kinetics — the outcome depends on concentration multiplied by time, the same way ceviche depends on lime and minutes. Stop the course early because the ulcer closed, and the center is still raw; the parasites at the base of the lesion are the last to be cured.
Chagas disease tells the same story with different props. The bug that carries Trypanosoma cruzi is known in Arequipa and the southern Andes as the chirimacha — it lives in adobe walls and feeds at night on sleeping faces. There is no reliable national count of infected Peruvians; house-to-house studies in Arequipa keep finding infection in a small but stubborn share of residents and their dogs. Our treatment is benznidazole, a drug registered in the 1970s. The largest trial ever run in chronic Chagas — the BENEFIT study, published in the New England Journal of Medicine in 2015 — found that benznidazole did not halt the progression of established heart disease. Read that carefully: it is not proof the drug is useless, because earlier-stage trials show benefit at earlier stages, but it took until 2015 to learn, with a 1970s drug, what decades of underfunding had left unknown.
Then there is the most Peruvian disease of all: Carrión’s disease, caused by Bartonella bacilliformis and transmitted by sandflies in inter-Andean valleys. Daniel Alcides Carrión, a medical student in Lima, inoculated himself in 1885 to prove that Oroya fever and verruga peruana were two phases of one disease, and died for it. More than a century later there is still no vaccine, and treatment still rests on chloramphenicol — in clinical use since the late 1940s — plus fluoroquinolones. In global funding tables, Carrión’s disease barely appears as a line item at all.
Dengue, in 2023, gave us absolute numbers worth memorizing. Peru logged more than 250,000 cases and roughly 400 deaths that season — on the order of one death for every 700 reported cases, concentrated in Piura, Loreto and Ucayali. Among patients who reached a hospital with warning signs, the risk was many times higher; among the hundreds of thousands with mild courses, near zero. Both numbers are true, and both belong in the sentence. Notice, too, that dengue is comparatively the rich cousin of this family: it appears in the G-FINDER tables with one of the largest single-disease totals, because it threatens middle-income countries as well. The diseases that hit only the poor, like the kinetoplastid infections — leishmaniasis and Chagas, named for the clump of mitochondrial DNA called a kinetoplast — draw a fraction of that.
Lo que sabemos / lo que todavía no
This site always separates what is settled from what is not, so here it is in the two columns.
Lo que sabemos: The gap is real and repeatedly measured; G-FINDER has counted it, year after year, since 2008. The drug-dating exercise — most of our treatments are forty to eighty years old — is not rhetoric; it is a fact of the pharmacopoeia. And there have been genuine wins: the RTS,S malaria vaccine, whose development began in 1987 and which the WHO recommended in 2021 after more than three decades; fexinidazole for sleeping sickness, delivered in 2018 by the Drugs for Neglected Diseases initiative; a dispersible pediatric formulation of benznidazole; and shorter, oral treatments for visceral leishmaniasis in South Asia and East Africa.
Lo que todavía no: How many Peruvians actually carry T. cruzi — the surveillance does not exist to say. Whether recent funding upticks will survive the next global financial cycle. How much of the dengue line displaces funding for other NTDs rather than adding to it. And, embarrassingly for a century-old field, the long-term safety of several old drugs still in standard use, because the post-approval studies were never funded either. When someone quotes you a precise figure for any of these, ask what the denominator was and who counted it.
El reclamo de la semana: does papaya leaf cure dengue?
Every week this column takes one persistent local claim and reads it mechanism-first. This week, in the middle of dengue season logic: the belief, repeated in markets from Piura to Iquitos, that papaya-leaf juice cures dengue by raising platelets.
The mechanism is not absurd, which is what makes the claim durable. Papaya leaves (Carica papaya) contain carpaine and other alkaloids plus papain-family enzymes, and several small human studies — from Sri Lanka, Malaysia and India, with Latin American series alongside — have reported faster platelet recovery in patients drinking leaf extracts. Platelets do fall in dengue, and a low platelet count is what families fear most.
But here is where the claim breaks. Dengue kills through vascular leakage and shock, not through the platelet number itself; a rising platelet count is a sign of recovery, not its cause. And no adequately large, adequately controlled trial has shown that papaya leaf changes the outcomes that matter — progression to severe disease or death. Small studies with a few dozen patients each cannot answer that question; they mostly measure a lab number over a few days, without blinding.
Blunt label, as this column always gives: there is no evidence that papaya leaf cures dengue or prevents severe disease. What the evidence supports is early medical evaluation, hydration, and knowing the alarm signs — abdominal pain, persistent vomiting, bleeding from gums or nose, lethargy, and a falling trend in the days after the fever breaks. Papaya-leaf juice is not dangerous the way a wrong drug is, but a family waiting on juice instead of watching for alarm signs can lose the window that saves a life.
And notice the funding thread running through this. Papaya is cheap, local, and answerable — a decent randomized trial in Piura or Iquitos would settle the question. It has never been properly funded. That is the 10/90 gap measured in a single leaf.
What Actually Moves the Needle
The gap is not a law of nature, and we know something about what closes it. Funding people talk about push and pull incentives. Push means paying for the work directly: grants, public laboratories, tax credits. Pull means making the finish line valuable: guaranteed purchase, prizes, faster review of the next product. The clearest proof of both is the product development partnership, or PDP — a not-for-profit that runs drug development the way a company does, with candidate molecules, clinical trials and regulatory files, but with public and philanthropic money and prices set near cost.
A PDP works like the starter in a chicha de jora fermentation. No single household keeps a pure yeast culture; the community shares a starter, and every family’s brew depends on it. The Drugs for Neglected Diseases initiative — founded in 2003 out of Médecins Sans Frontières — is that shared starter for the kinetoplastid diseases, and the Medicines for Malaria Venture plays the same role for antimalarials. Pool compound libraries, share trial networks, publish the failures, and suddenly the route exists even though no single passenger could have paid for it.
Pull incentives can be startlingly concrete. The United States created a priority review voucher in 2007: win approval for a neglected-disease drug, and you receive a voucher that speeds regulatory review of any other drug you own. Vouchers have changed hands for prices above US$100 million — a way of making a Chagas approval valuable to a company whose profits come from elsewhere.
And the part that concerns us here: the gap narrows fastest when endemic countries can run their own science. Peru has real anchors — the Alexander von Humboldt Institute of Tropical Medicine, the long tradition at the Universidad Peruana Cayetano Heredia, the surveillance teams at the Instituto Nacional de Salud. What is thin is the sustained national money that lets those teams ask and answer their own questions: research funds that arrive on schedule, biostatistics capacity, clinical trial units in Loreto and Cusco, and publication in both Spanish and English so the work is findable in Iquitos and in Geneva alike.
Frequently Asked Questions
What is the 10/90 gap in simple terms?
It is the mismatch between where the world’s disease burden sits and where its research money goes: roughly 10% of global health research funding has targeted the diseases responsible for about 90% of avoidable death and disability. The phrase comes from the Global Forum for Health Research in the late 1990s, and modern accounting by G-FINDER shows the pattern persisting.
How much does the world spend on neglected tropical disease research?
Around US$4 billion per year on all neglected diseases combined, against well over US$200 billion in annual pharmaceutical R&D. Of 1,393 new drugs marketed between 1975 and 1999, sixteen targeted tropical diseases or tuberculosis.
Why are there no new drugs for Chagas disease or leishmaniasis?
Because the people who need them mostly cannot pay market prices, so the expected return never justifies the cost of development, which runs from hundreds of millions to over a billion dollars per medicine. The result: benznidazole from the 1970s and antimonials from the 1940s are still standard care in 2025.
Does papaya leaf cure dengue?
No. Small studies report faster platelet recovery, but platelet count is a sign of recovery, not its cause, and no large controlled trial has shown the extract prevents severe dengue or death. What works is early evaluation, hydration and rapid response to alarm signs.
What is being done to close the gap?
Product development partnerships develop medicines with public and philanthropic funding; push mechanisms (grants, public labs) and pull mechanisms (purchase guarantees, priority review vouchers) reshape incentives; and stronger research capacity in endemic countries keeps the questions — and the answers — closer to the patients.
If a term here was new to you — 10/90 gap, DALY, R&D, kinetoplastid, PDP — it now has an entry in our growing Spanish-English glossary, and this piece has a Spanish version on the site as well. If there is a health claim from your market, your kitchen or your abuela’s shelf that deserves the mechanism-first reading, send it in. That queue is where half of these articles come from.
— Dra. Luz Mendoza, Universidad Nacional Agraria La Molina, Lima