herpesvirus

Herpesviruses are a large family of enveloped double-stranded DNA viruses (Herpesviridae) known for establishing lifelong latent infections and the ability to reactivate after the initial illness. The family includes eight human pathogens: herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), Epstein-Barr virus (EBV, HHV-4), cytomegalovirus (CMV, HHV-5), human herpesviruses 6 and 7 (HHV-6 and HHV-7), and human herpesvirus 8 (HHV-8, Kaposi sarcoma-associated virus). They infect a wide range of hosts and tissues, and their genomes are relatively large, encoding numerous proteins that regulate replication and latency.

Structure and life cycle: Herpesviruses are icosahedral, enveloped particles with linear dsDNA genomes. After primary infection, they establish latency in specific cell types (for example, HSV in sensory neurons, EBV in B cells, VZV in neurons). Latent genomes persist with limited gene expression and can reactivate under stress, illness, or immunosuppression, leading to recurrent or disseminated disease. Transmission routes vary by virus and include direct contact with lesions, saliva, respiratory droplets, sexual contact, or vertical transmission from mother to fetus or newborn.

Clinical features: HSV-1 and HSV-2 commonly cause oral and genital lesions, respectively. VZV causes varicella (chickenpox) and can reactivate as herpes zoster (shingles). EBV is associated with infectious mononucleosis and certain cancers; CMV can cause congenital disease and severe infections in immunocompromised individuals. HHV-6/7 are linked to roseola in children, and HHV-8 is associated with Kaposi sarcoma.

Diagnosis and treatment: Diagnosis uses PCR for viral DNA, serology, and, less commonly, culture. Treatments include antiviral nucleoside analogs such as acyclovir, valacyclovir, and famciclovir for HSV and VZV; ganciclovir and valganciclovir for CMV. Vaccines exist for VZV (varicella and shingles) but not broadly for HSV or CMV. Prevention relies on standard infection control, safe-sex practices, and targeted antiviral prophylaxis in high-risk individuals.