Why are viruses an exception to the cell theory?

Viruses are exceptions to the cell theory because they do not have a nucleus, organelles or other internal structure.

The cell theory states that all organisms are made up of cells, which are subatomic particles that carry out simple functions. The theory also says that cells have a nucleus, an organelle called the mitochondria and a double membrane.

Viruses do not have any of these features. They only have nucleic acid, no organelles, no mitochondria and no double membrane.