Infectious Processes and Medical Geology

Infectious disease in humans are acquired in particular environments that favor the interaction between a pathogenic microorganism and a susceptible human host. These environments are not constant, and geologically driven changes result in varying transmission environments that favor the development of specific disease patterns. This article outlines human exposure to potential pathogens in such environments from the earliest microbial life on Earth to the possible encounter of humans with extraterrestrial microbes. Examples are provided of diseases for which there exists a well-documented relationship between the infectious process and the geosphere, of which some are discussed in detail including coccidioidomycosis, tetanus, cryptosporidiosis, arboviral infection, tuberculosis, and others. Much of this infectious disease burden can be attributed to changes in the geosphere that humans have caused themselves, and reducing the future health impact of such anthropogenic changes is therefore one of the multidisciplinary challenges facing medical geology.