FIG. 2.

Schematic drawing of budding and fusion. Budding induces thickening of the membrane that is pulled behind the capsid. The space between capsids and the envelope is progressively filled by tegument. The resulting virion is finally released by fission. Fusion starts by close apposition of the virion to the membrane followed by pore formation between the envelope and the membrane. Capsid and tegument are rapidly released, and the membrane is flattened because there are no forces to keep it bent. The thickened membrane would persist at the entire length equaling the viral surface.