Infectious disease expert Timothy Endy, MD, MPH, was included among a research team that found evidence of a role for neighborhood immunity in determining risk of dengue infection, demonstrating that local variation at spatial scales of just a few hundred meters can significantly alter the risk of infection, even in a highly mobile and dense urban population with significant immunity. The team published its findings in the May 28 edition of the journal PNAS (Proceedings of the National Academy of Sciences of the United States of America). Dr. Endy is division chief of Infectious Disease, professor of medicine, associate professor of microbiology and immunology and of public health and preventive medicine. Dengue is caused by any one of four related viruses transmitted by mosquitoes. Although it rarely occurs in the continental United States, it is endemic in Puerto Rico, and in many popular tourist destinations in Latin America and Southeast Asia; periodic outbreaks occur in Samoa and Guam.