Other discoveries have been counterintuitive: Koelle's lab found that partially controlling mosquitoes can lead to more deaths from dengue hemorrhagic fever, not less. When mosquito populations were diminished but not destroyed, the number of dengue hemorrhagic fever cases actually increased. With fewer mosquitoes around, Koelle explains, people weren't getting re-infected until their initial antibodies had decayed. Koelle hopes such knowledge can guide public policy, pointing to new strategies for containing emerging diseases. And as viruses continue to evolve rapidly with the world around us, she plans to stay a step ahead.