The disease of malaria is triggered by single-celled parasites that accumulate in large groups in the salivary glands of mosquitoes before transmission to human beings. The limited space there prevents them from actually moving, unless this restriction is lifted by means of appropriate experimental preparation. In just such a set of experiments, researchers at Heidelberg University have set the pathogens in motion and analyzed the acquired image data using cutting-edge methods of image processing. The data show that the collectively moving pathogens form vortex systems that are largely determined by physical principles. Special computer simulations helped identify the mechanisms underlying these rotating movements.