CBSE Class 9 Answered

Viruses usually do not have a cell membrane, they only have a protein coat called capsid. Only enveloped viruses have a membrane that has been derived from the host cell membrane.
The viral envelope can give the virus a few distinct advantages such as protection from enzymes and certain chemicals. Most enveloped viruses are dependent on the envelope for infectivity. Since the virus has the cells own envelope, the body may not recognize it as foreign which allows it to escape detection until it is too late. Viruses without cell membranes derived from host, are easier to detect by the immune system of the body.