Malaria is an infectious disease caused by a parasite: it is spread by the bite of an infected mosquito. People catch malaria when the parasite enters the blood. The parasite causes a deadly infection which kills many people each year (from 75 million cases in 1950s to 0.1 million cases in 1960s). However, due to the development of insecticide resistance among mosquitoes and other factors, it staged a comeback in the mid 1970s (6.47 million cases in 1976), and continues to prevail in endemic/subendemic proportions, so that 80% indian population lives in malaria risk areas.