I love looking at infection maps. Hat-tip to Michael Walsh at Germscape for finding this map. There is a lot of information on this map and unfortunately any text that might have come with it at Lapham’s Quarterly is not readily available. So we have the map to figure out without any explanation. The red arteries represent the origin of Leprosy in central Africa and the blue veins represent the origin of smallpox in northern Africa and its spread. Transmission lines for malaria are not shown; the yellow areas seem to represent modern endemic malaria. The geographic highlights either document transmission events or major steps in the study of malaria, smallpox and leprosy.
At the height of its expansion, there are few places on earth that malaria did not penetrate. Today malaria is found primarily in tropical regions but that wasn’t always so. The map to the right illustrates the malarial deaths listed in the 1870 US federal census. Malaria once was endemic, at one time or another, in most of the United States east of the Mississippi River and around the Gulf of Mexico. Likewise it was endemic in parts of 19th century Britain. In temperate regions of the world it is the humans who carry the parasite through the winter and infect the spring mosquitoes. Contrary to general knowledge, most malaria in the United States dwindled long before the arrival of DDT. Improving the standard of living and eliminating unnecessary standing water are the most important ways to decrease malaria. Early American physician Benjamin Rush knew this over two centuries ago.