Malaria is serious business. This disease, which is transmitted by infected mosquitoes, kills hundreds of thousands of people each year and infects millions, mostly in sub-Saharan Africa. Since the turn of the 21st century, advances in disease control have cut the global rate of infection by more than 60 percent. Long-lasting insecticide nets (LLINs), which form a physical barrier around a person’s bed with the added protection of a chemical coating, have been particularly effective. But a recent trial in Uganda reminds us that mosquitoes are quick to adapt.