New research elucidates the mechanism of sexual transmission of filoviruses, which have been shown to persist in the testes and other immune privileged sites. Sexual transmission of filoviruses was first reported in 1968 after an outbreak of Marburg virus disease and recently caused flare-ups of Ebola virus disease in the 2013-2016 outbreak. The team found that Marburg virus persists in seminiferous tubules and that Sertoli cells are the reservoir for the virus.