Herpesvirales

Herpesvirales is an order of large, enveloped double-stranded DNA viruses that infect a wide range of hosts, including vertebrates, molluscs, and fish. It comprises three families: Herpesviridae, Alloherpesviridae, and Malacoherpesviridae.

Virions are large icosahedral particles with an outer envelope and a tegument layer. Their genomes are linear double-stranded DNA, typically 120 to over 200 kilobases, encoding dozens to more than a hundred genes. The virions replicate in the host cell nucleus and use the viral replication machinery for DNA synthesis.

The replication cycle features immediate-early, early, and late gene expression. Assembly occurs in the nucleus with subsequent envelopment and release by budding. Many herpesviruses establish lifelong latent infections, often in neurons or lymphoid cells, with periodic reactivation causing recurrent disease.

In humans, members of Herpesviridae cause diseases ranging from oral and genital lesions to chickenpox and mononucleosis. Alloherpesviridae and Malacoherpesviridae include important pathogens of fish and molluscs, impacting aquaculture and wildlife. Vaccines and antiviral strategies are active areas of research, reflecting the medical and economic significance of members across the order.