Viruses such as HIV-1 replicate by invading and hijacking cells, forcing the cells to make new copies of the virus. These copies then leave the cell and continue the infection by invading and hijacking new cells.There are two ways that viruses may move between cells, which are known as ‘cell-free’ and ‘cell-to-cell’ infection.In cell-free infection, the virus is released into the fluid that surrounds cells and moves from there into the next cell.ell-to-cell infection by HIV contributes over half of virus infection. (2015) eLife 4: e08150 doi: 10.7554/eLife.08150. Cell-to-cell viral infection, in which viruses spread through contact of infected cell with surrounding uninfected cells, has been considered as a critical mode of virus infection.