What components must a virus have at minimum?

A virus must, at minimum, consist of a capsid and genetic material. The capsid is a protein coat that encases and protects the viral genome, which can be either DNA or RNA. This combination is essential because the capsid provides structural integrity and aids in the delivery of the viral genome into host cells. The genetic material contains the necessary information for the virus to replicate and produce new virions once inside a host.

A nucleocapsid is indeed a vital structure, as it combines the nucleic acid and the protective protein coat, but it does not describe the requirement separately as both components are crucial in their individual forms. While a lipid envelope can be present in some viruses (enveloped viruses), not all viruses have this feature; thus, it is not a minimum requirement for the functioning of a virus. Hence, the most foundational components needed for a virus to exist and operate are the capsid and the genetic material.