Cali, Colombia, my home for the past decade, is often ranked among the most violent cities on the planet. The most common way for an adult male to die in the city is from a bullet. Yet when I walk the streets of my adopted city during the day, I feel quite safe. It is only when the sun goes down and a cool breeze comes down from the mountains, awakening the little creatures that live in this lush, tropical city, that I fear for my life.

Each year, over four hundred thousand human beings on this planet are murdered by other human beings. Much more deadly, however, is a nearly invisible predator responsible for the annual deaths of over a million people, a predator that by some estimates has killed, since human history was recorded, a total of over fifty billion human beings — almost half of all those who have ever lived. This deadly assassin is, of course, the mosquito.