Significance Satellites are virus-like agents which require both a host and a virus to complete their life cycle. The only human-infecting satellite is hepatitis delta virus (HDV), which exacerbates liver disease in patients co-infected with hepatitis B virus (HBV). How HDV originated is a long-standing evolutionary puzzle. Using terabase-scale data mining, coevolutionary analyses, and field studies in bats, we show that deltaviruses can jump between highly divergent host species. Our results further suggest that the contemporary association between HDV and HBV likely arose following zoonotic transmission from a yet-undiscovered animal reservoir in the Americas. Plastic host and virus associations open prospects that deltaviruses might alter the virulence of multiple viruses in multiple host species.