Solution:

Viruses are infectious organisms that, when located outside the host cell, solidify in structure. The genetic material is either DNA or RNA (but never both), and it is found inside the protein core. Viruses that infect plants have single-stranded RNA, while those that infect mammals have single-stranded DNA or RNA. The capsid is a protein coat that protects nucleic acid and is made up of tiny subunits called capsomers.

Influenza, AIDS, Herpes, and Rabies are some of the most common viral infections.