EDITOR’S NOTE: We now know that a single-celled sporozoan of the Plasmodium genus causes malaria. It was discovered to be a parasite in 1880, by Alphonse Laveran, a French army surgeon in Algeria, and its transmission by the mosquito was first demonstrated in 1897 by Ronald Ross, a British officer in the Indian Medical Service. As you read this article you sense the struggle to understand the parts of the puzzle of this disease (and other diseases transmitted also by mosquitoes and bad hygiene). With our hindsight from 2011 we can quickly grasp that it is the terrain most favorable to mosquitoes that tends to be the most prone to malaria.