Heat stress: the next global public health crisis?

The deaths of farm workers in Central America are being linked to extreme temperatures. Researchers warn that far worse is to come

• The sugar cane workers of Nicaragua and El Salvador - in pictures

When rural labourers first started turning up at the Rosales National Hospital in the El Salvadorian capital of San Salvador with advanced symptoms of chronic kidney disease (CKD), doctors put the phenomenon down to pesticides. Their latest thinking is simpler: it's the heat.

Ramon Garcia Trabanino, president of the Association of Nephrology of El Salvador and a leading expert on CKD, describes it as a "silent disease" as it presents no symptoms until it's at an advanced stage. CKD, which has no known cure, is affecting thousands of people in Central America, with an estimated 20,000 deaths in the last two decades.