More than half the world's population is at risk from dengue fever, a viral infection that is spread via the bite of an infected mosquito. While some cases of the disease can be mild, others can be extremely dangerous and even fatal - particularly if someone has contracted the virus previously. When cases of dengue fever are high, those at risk can take some preventative measures, such as wearing clothing that covers as much skin as possible, using mosquito nets at night, and avoiding standing water. As such, some way of predicting high levels of the virus before they arrive would be invaluable. This is exactly what Dr Sarah Sparrow and her colleagues at the DART (Dengue Advanced Readiness Tools) project are hoping to achieve - using climate data to create a forecast, similar to a pollen forecast, for dengue fever.