Malaria, a parasitic disease, is the unsurpassed scourge of humankind. Dr. W. D. Tiggert, an early malariologist at Walter Reed Army Medical Center, said, “Malaria, like the weather, seems to have always been with the human race.” He continued, “And as Mark Twain said about the weather, it seems that very little is done about it.” Even today, more than 200 million unlucky people contract malaria each year.

Malaria often produces a synchronized and cyclical pattern of symptoms: a cold stage of chills and shakes, followed by a hot stage marked by fevers, headaches and vomiting, and finally a sweating stage. After a period of respite, this progression repeats itself. For many, especially children under 5, malaria triggers organ failure, coma and death.

Mosquitoes also transmit a catalog of viruses: dengue, West Nile, Zika and various encephalitides. While debilitating, these diseases are generally not prolific killers. Yellow fever, however, is the viral exception. It can produce fever-induced delirium, liver damage bleeding from the mouth, nose and eyes, and coma. Internal corrosion induces vomit of blood, the color of coffee grounds, giving rise to the Spanish name for yellow fever, vómito negro (black vomit), which is sometimes followed by death.