The viral replication process begins when a virus infects its host by attaching to the host cell and penetrating the cell wall or membrane. The virus's genome is uncoated from the protein and injected into the host cell.
Hence, during infection in vivo, a noncytopathic virus may turn off the "differentiation" or "luxury" function of a cell while not killing that cell (loss of vital function). This is turn can disrupt homeostasis and cause disease
