Geography of Infectious Diseases

• The geography of many infections is dynamic. • Biological characteristics of organisms, human and animal host factors, and bioclimatic factors influence where diseases occur. • Diseases vary in their potential to be moved from one area to another. Those with a fixed focal distribution often require a specific arthropod vector or intermediate host – or require special geoclimatic conditions. • The speed, volume and reach of travel and migration and trade have influenced the geography of infectious diseases and facilitate rapid changes in distributions. • The burden from diseases with a global distribution varies greatly from one population to another and is influenced by socioeconomic, demographic, bioclimatic, environmental, host genetics and other factors. • The urban population growth in tropical low- and middle-income regions places large, dense human populations with limited resources in geographic sites with high biodiversity and risk for many infections. • Alternative or unusual routes of transmission (e.g. organ or tissue transplantation) can lead to appearance of diseases outside of usual distributions.