One million people die of malaria every year. The disease, spread by a tropical mosquito to more than 200 million people annually—mostly children—is caused by a group of related parasites that use the mosquitoes to travel from patient to patient. Four of these parasites are responsible for most malaria cases among humans; two of them cause mild illness which rarely leads to death, while the other two are the most commonly fatal varieties. A fifth kind found in Asia generally infects macaques but can occasionally spread to humans. Malaria is not directly contagious, but when a female Anopheles mosquito bites someone infected with one of the types of malaria, she picks up the pathogen, and other people she bites afterward then become infected themselves.
These mosquitoes, scientists have found, target humans specifically, looking for human odors and heat patterns. The insects deliberately aim at whatever smells human—indeed, mosquitoes carrying malaria are even more attracted to humans than mosquitoes that are not—and has normal human body temperature, meaning traps and other things that lure them away from human beings ought to resemble humans in both ways; the researchers suggested that the odor traps typically used be supplemented with a heat source.
Another study also found that the microbes themselves plan and coordinate their attacks, communicating among themselves to ready each other to be picked up by mosquitoes. When it’s time for the mosquitoes to come, the parasites in the blood send each other information so they know to get ready, and enter a phase of their life cycle most conducive to being transmitted into another host.
There is no malaria vaccine, though research is ongoing. The recent discovery that the parasite attaches itself to blood vessel walls is a big step forward in malaria prevention, providing researchers looking for a vaccine with a possible research angle. Malaria prevention today focuses on encouraging the use of insecticide to get rid of mosquitoes entirely or netting to keep them away from people, particularly while they’re sleeping.