Grand rounds: The opportunity for and challenges to malaria eradication.

In 2009, malaria, a disease transmitted by the bite of an infective Anopheles mosquito, caused an estimated 225 million clinical cases and 781,000 deaths worldwide, of which more than 90% occurred in children aged <5 years in Africa. Approximately half of the world's population, or 3 billion persons, are at risk for acquiring the illness. Malaria is transmitted most intensely in central and western Africa, where in some areas >40% of children aged <10 years are infected and residents can be bitten by more than one infective mosquito every day of the year.