MARV infected cells develop viral inclusions in the perinuclear region [19, 20, 21] . These contain NC proteins and are most likely centres of NC assembly [22] . MARV particles bud from the plasma membrane (PM) of long filamentous cellular protrusions that contain parallel actin bundles and other markers of filopodia [23] . The released virus particle has a membrane envelope and contains an NC that is surrounded by the viral matrix protein VP40. It is unclear how NCs are transported from viral inclusions to the PM, whether they adopt their virion conformation before, during, or after, transport, or where NCs associate with VP40 that is not co-transported with NCs but is necessary for budding. Released MARV particles appear filamentous, hooked, six-shaped or round by electron microscopy (EM) [24] but their three-dimensional (3D) morphology is unclear. It is also unknown whether production of differently shaped viruses depends on different budding mechanisms and whether they differ in infectivity. Experiments to address these issues are complicated by the need to perform all infection experiments under BSL-4 containment conditions.