The virus HTLV-1 is thought to pass between cells through synapses formed when infected lymphocytes make contact with other T cells. Isabelle Thoulouze and her colleagues uncover an alternative mechanism for the cell-to-cell transmission of this virus. They show that HTLV-1 virions bud at the plasma membrane and are held at the cell surface in structures reminiscent of bacterial biofilms. When infected lymphocytes make contacts with other cells, the adhesive viral assemblies are rapidly transferred to to the surface of the new lymphocyte, from which the virions mediate a new round of infection.