INFECTED SALIVA

A female mosquito has mouthparts adapted for cutting through human skin. When searching for a blood vessel, the mosquito squirts saliva into the wound, sometimes transferring malarial parasites or the viruses that variously cause yellow fever, dengue, Zika, chikungunya, or West Nile disease. The mosquito bears its victim no ill will, of course: It injects saliva because the anticoagulant properties keep the blood flowing, ensuring the mosquito gets a hardy meal. But an estimated 700 million people per year fall victim to a mosquito-borne disease, and up to a million of them die from malaria alone, making mosquitoes humankind’s most dangerous predator. As the climate continues to warm, mosquitoes threaten more and more people.