ERVW-1 and infection: Here we describe novel elements: (1) contact between infected and uninfected cells may result in cell fusion, viral transmission without cell fusion, or the absence of viral transmission and/or productive infection; (2) Env accumulation at a synapse-like structure is not observable at the contact zone between cells; and (3) the frequently occurring intercellular connections mostly result from infected and/or uninfected cells moving apart after having been in contact.