Each year half a million people in India and other tropical countries catch visceral leishmaniasis, also known as black fever. Infected by the bite of a sand fly, they rapidly weaken and lose weight before dying with painfully swollen livers and spleens.

A safe and effective treatment for black fever was found long ago: the antibiotic paromomycin (cure rate 95%). But the firm that developed it -- Pharmacia, a precursor of Pfizer – shelved it in the 1960s for lack of a "viable market." What that means is that the people who need it cannot afford to pay for it. It is simply not profitable for pharmaceutical companies to fight diseases that afflict the poor. Less than 1% of the new drugs developed in 1975–99 were for tropical diseases (Joel Bakan, The Corporation: The Pathological Pursuit of Profit and Power, Simon & Schuster 2005, p. 49).