Shortly after HDV was discovered, researchers were surprised to find it on every populated continent of the world. While it is worldwide in scope it is defiantly concentrated more in some areas than in others. One major hotspot for HDV is the indigenous peoples of Venezuela, Colombia, Brazil, and Peru. The method of transmission in this setting is poorly understood but believed to involve intimate contact under conditions of poor hygiene. In developed nations, the high-risk populations are similar to that for HBV and HIV: hemophiliacs, users of illicit parenteral drugs, and others exposed to blood or blood products. The fact that it is relatively less common than HBV or HIV among groups of sexually promiscuous homosexual and heterosexual groups indicates that it is not typically a sexually transmitted disease.
The epidemiology of HDV, which is mostly transmitted by blood and blood products, is not conductive to epidemics in the classical sense. However, there are some exceptions to this. Contamination of clotting factor with HDV in past years has led to a epidemic of sorts. Also, there are occasionally small epidemics among drug addicts and some European populations of drug users have had prolonged epidemics after HDV was introduced.