Atypical viruses are a type of virus that have unique properties that make them different from other viruses. These viruses can be classified into several different categories, including:
1. Unicellular viruses: These are viruses that contain only one cell, such as the herpes virus, HIV, and hepatitis B virus. Unicellular viruses do not replicate within a host cell, but instead they can remain dormant for long periods of time before they become active again.
2. Multicellular viruses: These are viruses that contain more than one cell, such as the adenoviruses and papillomaviruses. Multicellular viruses can replicate within a host cell and cause infection.
3. Prion-like viruses: These are viruses that lack a nucleic acid core, such as the Borna virus. Prion-like viruses are not able to replicate within a host cell, but instead they are capable of attaching themselves to the host’s cells and inducing changes in the host's cells.
4. Retroviruses: These are viruses that contain an RNA genome, such as HIV. Retroviruses are able to replicate within a host cell and can cause infection.
5. Satellite viruses: These are viruses that require the presence of another virus for their replication, such as the BK virus. Satellite viruses are not able to replicate on their own and must rely on another virus for their replication.
6. Viroids: These are small strands of RNA that lack a nucleic acid core, such as the potato spindle tuber viroid. Viroids are not able to replicate within a host cell, but instead they can cause infection by attaching themselves to a host cell.
7. Chimera viruses: These are viruses that contain two or more different nucleic acid molecules, such as the mouse mammary tumor virus. Chimera viruses are able to replicate within a host cell and can cause infection.