BHK cells transfected with a dually labeled (nsP3-eYFP/mCherry-E2) E1 fusion loop mutant (G91D) demonstrated that particles released from transfected cells can enter uninfected neighboring cells (Fig. 7D) via endocytosis but cannot fuse to the endosomal membranes to initiate a productive infection (see Movie S4 in the supplemental material). The gene discussed is SH2D3C; the disease is infection.