Scientists have found a telltale molecular marker for Onchocerciasis or “river blindness,” a parasitic infection that affects tens of millions of people in Africa, Latin America and other tropical regions. The newly discovered biomarker, detectable in patients’ urine, is secreted by Onchocerca volvulus worms during an active infection. The biomarker could form the basis of a portable, field-ready test with significant advantages over current diagnostic methods.