The work “shows that light pollution is not only bad for our [daily rhythms], but also can affect disease prevalence and transmission,” says Jenny Ouyang, an integrative physiologist at the University of Nevada in Reno. “Perhaps infection in humans and other animals is also affected by light,” adds Yale University epidemiologist Durland Fish. (Neither Ouyang nor Fish were involved in the study.) West Nile is primarily a bird virus, but people occasionally get infected because some bird-biting mosquitoes dine on human blood as well. Human infections can cause fevers, body aches, rashes, diarrhea, long-term fatigue, and, in some cases, inflammation of the brain and its membranes. In the United States, almost 2000 people have died from West Nile since its arrival.