Light pollution increases the risk of West Nile virus

Florida experienced a relatively mild winter, which usually translates to more mosquitoes in the summer and more birds that they can feast on. If history repeats itself, there is likely to be an increase in cases of West Nile virus this year, especially in the suburbs, where much of the night lighting emanates from the brightness of the skies in nearby cities.

A new study from the University of South Florida (USF) is the first to provide direct evidence that light pollution is driving patterns of infectious diseases in nature. The research team previously determined that mosquitoes and birds are attracted to light, greatly increasing the likelihood of spreading West Nile virus to animals and humans. His new findings published in the Proceedings of the Royal Society B they are in contrast to previous studies that blamed urbanization due to the density of the human population and critical points of reproduction, such as drainage systems.

“We knew that light pollution could affect immune defenses and host behavior,” said lead author Meredith Kernbach, a doctoral student at the USF School of Public Health. “But what we didn’t know until now is that light pollution can significantly affect when and where West Nile virus appears in nature.”

The research team, which includes collaborators from the University of Georgia and California Polytechnic State University, modeled the Florida Department of Health’s West Nile virus exposure data. They studied 6,468 sentinel antibody samples collected between June and December over four years in 105 cooperatives across the state. The researchers found that the majority of West Nile virus cases were present in chickens exposed to low light levels compared to those surrounded by areas that are unpolluted and heavily polluted by light.

“We think we peaked at low light levels because of the many ways in which light pollution is likely to pose a risk of infection,” said Marty Martin, professor of disease ecology at the USF Center for Global Health and Infectious Disease Research. . “Based on previous work, we know that light pollution affects birds’ immune responses to West Nile virus, but there is probably also an effect on mosquito abundance, as most insects are attracted to light. Even birds can be attracted to places polluted by light, as food could be more abundant or obvious there. Perhaps all of these forces coming together is what increases the risk in places with light pollution. “

Many county health departments use sentinel hens as a surveillance mechanism to monitor West Nile virus and other mosquito-borne diseases. They are usually not sick with the virus and cannot pass it on to mosquitoes, people or other birds. Counties strategically place cages in locations that best represent the local human population, helping to identify where to target mitigation efforts that can prevent the spread of infection.

These findings support a 2019 USF study that found that exposure to artificial light increases the infection period for wild birds, increasing the potential for West Nile virus outbreaks by 41 percent.