Malaria draws mosquitoes to infected humans, and vice versa 

Sarah Zhang at the Atlantic writes about an interesting new discovery: The molecule that draws mosquitoes to infected humans, and causes infected mosquitoes to be more hungry for blood, known as HMBPP:

The discovery came by accident. Ingrid Faye, a molecular biologist at Stockholm University, was curious about a particular molecule made by malaria parasites called HMBPP. She wanted to drill into the details of how HMBPP affects mosquito immune systems, but her team ended up noticing some behavior too odd to ignore: The mosquitos—specifically, the species Anopheles gambiae they were studying—would go crazy for human blood with HMBPP. “The difference it made was just astounding,” says Faye. When given a choice between normal human blood and that either laced with the HMBPP or infected with malaria parasites, almost all the mosquitoes went for the latter two.

Source: The Parasite That Lures Mosquitos to Humans – The Atlantic