The deadliest animal in the world is smaller than a pencil eraser and weighs around two-thousandths of a gram - less than the weight of a single raindrop. These global shifts, which will only accelerate as the planet warms, have sparked concern that the diseases mosquitoes carry will exact an even higher toll in the months and years to come. But as urban heat islands expand and temperatures rise, mosquito-borne diseases are expected to travel outside of their typical regions. Malaria cases worldwide declined steadily for nearly two decades. The Anopheles mosquito carries malaria; the Aedes aegypti and the Aedes albopictus mosquitoes carry diseases like dengue and chikungunya.