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What is Viral disease and explain in detail?
A viral disease (or viral infection) occurs when an organisms body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells.

Structural Characteristics
Basic structural characteristics, such as genome type, virion shape and replication site, generally share the same features among virus species within the same family.
Double-stranded DNA families: three are non-enveloped (Adenoviridae, Papillomaviridae and Polyomaviridae) and two are enveloped (Herpesviridae and Poxviridae). All of the non-enveloped families have icosahedral capsids.
Partly double-stranded DNA viruses: Hepadnaviridae. These viruses are enveloped.
One family of single-stranded DNA viruses infects humans: Parvoviridae