Virus filament formation occurs on human metapneumovirus (HMPV)-infected LLC-MK2 cells. Confocal microscopy imaging of HMPV-infected LLC-MK2 cells (at 10 days post-infection) probed with (A) anti-M, anti-F and anti-G (green). The cells were also co-stained using Evans Blue (red). (B) Cross-section image of anti-G stained HMPV-infected LLC-MK2 cells showing virus filaments. In each case the virus filaments are indicated (white arrows).