María Guzmán, author of this month's essay, is head of the virology department at the Tropical Medicine Institute Pedro Kourí (IPK), in Havana, Cuba. Her work on dengue viruses in Cuba and abroad has contributed to knowledge of the diagnosis, epidemiology, and clinical progression of this disease. She is director of the PAHO/WHO Collaborating Center for Viral Diseases and a Fellow of the Academy of Sciences for the Developing World.