The molecular mechanism lies in the nerve cells of the female Anopheles mosquito that help the insect to detect a human victim from miles away, the researchers report in Thursday's issue of Nature, the weekly British science journal.
An oderant in sweat called 4-methylphenol activates olfactory cells through a lock, or receptor, on those cells that is termed AgOr1. Once triggered, those cells then alert the mosquito to a potential meal.
The discovery has big potential, for it opens the way to a new generation of mosquito repellants that neutralise 4-methylphenol.
Alternatively, 4-methylphenol could be used to bait traps to lure mosquitoes to their death.
Only female mosquitoes carry AgOr1 - and female mosquitoes are the biggest carrier of the malaria parasite Plasmodium falciparum. It is passed on to humans when the mosquito takes a blood meal.
In the bloodstream it proliferates like wildfire and is passed on to other mosquitoes who feed on the same host, thus perpetuating the cycle.
The research was led by John Carlson of Yale University's Department of Molecular, Cellular and Developmental Biology.