THE WORLD OF VIRUS : Duplodnaviria.
Duplodnaviria is a realm of viruses encompassing all double-stranded DNA viruses that encode the HK97 fold major capsid protein (HK97 MCP), a key component of the viral capsid responsible for storing the viral deoxyribonucleic acid (DNA). Viruses within this realm share several distinct features, including an icosahedral capsid, a portal opening in the capsid, a protease enzyme that empties the capsid before DNA packaging, and a terminase enzyme that facilitates viral DNA packaging. Established in 2019, Duplodnaviria contains two primary groups of viruses: tailed bacteriophages of the order Caudovirales, which infect prokaryotes, and herpesviruses of the order Herpesvirales, which infect animals. Tailed bacteriophages, thought to be the oldest lineage of viruses, are widely distributed and crucial in marine ecology for recycling nutrients from their host organisms. Herpesviruses, on the other hand, are linked to a range of diseases in animals, including humans. A defining characteristic of viruses in Duplodnaviria is their ability to persist in hosts for extended periods without replicating, reactivating later. Notable examples include the herpes simplex virus, which causes recurring infections, and the varicella zoster virus, which leads to chickenpox and later reappears as shingles.