Malaria is caused by a parasite that lives in Anopheles mosquitoes. An infected mosquito can transmit the parasite to a human when the bug bites and its infected saliva mixes with human blood. Parasite resistance to antimalarial drugs is a serious concern. Scientists have recently developed a series of tests that rapidly detect resistance in malaria parasites. Researchers are also studying the role of hemoglobin C in the prevention of malaria. Studies in village populations have found that people with high concentrations of hemoglobin C in their blood are more resistant to the malaria parasite and less likely to develop or die from serious disease. Researchers are also developing field sites for the eventual testing of malaria vaccine candidates.