In the sugarcane fields of El Salvador, men like Oscar rise before dawn to swing machetes under an unforgiving sun. For decades, this brutal labour has quietly claimed lives, not with accidents or violence, but with failing kidneys. A mysterious epidemic of chronic kidney disease, now known as CKDu — chronic kidney disease of unknown cause — has swept through agricultural communities, striking down otherwise healthy men in their twenties, thirties, and forties.
First noticed in the late 1990s in the coastal region of Bajo Lempa, the disease has since spread across Central America and beyond. According to reporting in Nature, as many as one in four men in some areas of El Salvador suffer from kidney disease. And the epidemic is far from local. Cases now appear in Nicaragua, Costa Rica, Panama, Mexico, India, Sri Lanka, and even among migrant workers in the Middle East and the U.S.
Unlike typical kidney disease, CKDu isn’t tied to diabetes or high blood pressure. It targets those exposed to long hours of hard labour in extreme heat — sugar-cane cutters, rice farmers, construction workers, miners. Scientists now believe repeated dehydration and heat stress, compounded by poor nutrition, pesticide exposure, and lack of medical care, are driving this silent mass death.
Doctors were stunned when the first patients appeared. “It was a massacre,” said Ramón García-Trabanino, who encountered waves of young men arriving at El Salvador’s Rosales Hospital, already in kidney failure. There was no precedent in textbooks. No explanation. Just men who worked themselves to death.
New studies, highlighted in Nature, show that the kidneys begin to deteriorate from repeated minor injuries — injuries that used to be thought reversible. But if a worker suffers day after day in sweltering fields, with little water, rest, or shade, that damage accumulates. Eventually, the kidneys crash. Without dialysis — which many can’t access — death is inevitable.
Climate change is intensifying the crisis. Higher temperatures and more humid conditions are becoming normal. “This is the biggest story in the world about kidney disease,” says Emmanuel Jarquín, a Salvadoran physician fighting the epidemic. Researchers say this disease is a warning: a physiological time bomb triggered by heat, labour, and inequality.
In Sri Lanka, CKDu has been linked to pesticides that linger in mineral-rich groundwater. In Nicaragua and Mexico, sugary drinks used in place of clean water may worsen inflammation in kidneys. Ibuprofen, often used to numb pain from labour, may also accelerate damage. Nature reports that researchers are scrambling to find early biomarkers that can detect kidney injury before it becomes irreversible — but health systems in places like El Salvador are overwhelmed. In some towns, people can only get dialysis after someone else dies.
And yet, there is hope. With hydration, rest, nutrition, and early screening, the disease can be slowed. When Oscar went to the clinic in Tierra Blanca, he feared the worst. But the tests showed his disease was still mild. With simple changes — more water, more shade — he might live. “Gracias a Dios,” he said, smiling. “Thank God.”
But thousands of others may not be so lucky. As Nature warns, the world’s rising heat is not just uncomfortable — it’s lethal. And for many workers, it’s already too late.
