Bats in the tropics of the Americas are a reservoir for morbilliviruses—a genus of RNA viruses that includes the human measles virus. However, their role in spreading morbilliviruses to other mammalian species is unclear. An international team of researchers led by Charité – Universitätsmedizin Berlin and the German Center for Infection Research has now studied the spread of morbilliviruses in bats and monkeys in Brazil and Costa Rica and discovered new virus species and host switches from bats to other mammalian species. The scientists call for increased surveillance and experimental risk assessments of reservoir-bound morbilliviruses.