Hemophagous, ectoparasitical arthropod vectors transmit infectious diseases, and local inhabitants and travelers are often unaware of exposure. Early clinical awareness in regard to a possible transmission and to the important, regionally specific or dominant pathogens and vectors aids in the prevention or anticipation of a potentially severe course of illness. Two diseases are reviewed that are endemic over large regions and tend to a regional diversity concerning pathogens, severe disease highlights, and vectors, and this diversity is described: Malaria of the tropics and subtropics, borne by Anopheles mosquitoes, and tick-borne (ixodid-borne) flavivirus encephalitis of the temperate climate zone, specifically the tick-borne encephalitis (Eurasia) and the Powassan encephalitis (North America, Russia).