Herpeszvírus

Herpeszvírus, or herpesviruses, constitute a large family of enveloped double-stranded DNA viruses that infect humans and many other animals. They share the ability to establish latent infections in host cells and to reactivate, causing recurrent disease. The family is divided into three subfamilies: Alphaherpesvirinae (including herpes simplex virus 1 and 2, HSV-1 and HSV-2, and varicella‑zoster virus, VZV), Betaherpesvirinae (cytomegalovirus, CMV; and HHV-6 and HHV-7), and Gammaherpesvirinae (Epstein–Barr virus, EBV; and Kaposi sarcoma–associated herpesvirus, HHV-8). In humans, eight herpesviruses are commonly recognised (HHV-1 to HHV-8). Transmission occurs through close contact, saliva, sexual contact, respiratory droplets, or from mother to child.

Virions are large, enveloped particles with a icosahedral capsid containing linear double-stranded DNA. Replication occurs in the cell nucleus and proceeds through a gene-expression cascade of immediate-early, early and late genes. The capsid and tegument assemble in the nucleus and acquire their envelope as they exit the cell. A hallmark of herpesviruses is lifelong persistence in the host, with periods of latency in specific cells: sensory ganglia for HSV and VZV; monocytes and other cells for CMV; B- and T-cell lines for EBV and HHV-8—and periodic reactivation prompted by stress, immunosuppression or other triggers.

Clinical impact ranges from asymptomatic infections to serious disease. HSV-1/2 cause oral and genital lesions; VZV causes chickenpox and shingles; CMV, EBV and HHV-6/7 can contribute to mononucleosis-like syndromes and congenital or opportunistic diseases; HHV-8 is associated with Kaposi’s sarcoma. Vaccines exist for varicella and shingles, and antiviral drugs such as acyclovir, valacyclovir and famciclovir target viral DNA polymerase; ganciclovir treats CMV infections. Diagnosis relies on PCR-based detection of viral DNA, serology for antibodies, and tissue histology in some cases. Prevention focuses on minimizing exposure during active disease, good hygiene and, where available, vaccination. Because of latency, herpesviruses persist for life and recurrent disease is common.