Further highlighting the importance of IFITMs in virus producer cells in restricting viral infection, it is reported that IFITM3 in uninfected target cells does not inhibit HIV-1 infection when infection is mediated by co-cultured HIV-infected lymphocytes, while overexpression of IFITM3 in virus-producing lymphocytes and 293T cells restrict viral spread [101]. Here, IFITM3 is linked to viral infectious disease.