Herpesviruses
Also known as: herpesviridae, human herpesviruses
Herpesviruses are a family of enveloped, double-stranded DNA viruses that establish lifelong latent infections in humans. Members include HSV-1, HSV-2, varicella-zoster virus, Epstein-Barr virus, and cytomegalovirus.
Herpesviruses (family Herpesviridae) are large, enveloped, double-stranded DNA viruses with an icosahedral capsid. Their defining biological feature is latency: after the initial infection resolves, the viral genome persists in specific cell types for the host's lifetime and can reactivate later, especially during stress or immunosuppression.
Eight human herpesviruses are recognized. Herpes simplex virus 1 (HSV-1) causes oral herpes and is the leading cause of sporadic viral encephalitis; HSV-2 causes genital herpes; both remain latent in sensory neurons. Varicella-zoster virus (VZV) causes chickenpox, then reactivates from dorsal root ganglia as shingles. Epstein-Barr virus (EBV) causes infectious mononucleosis, remains latent in B cells, and is linked to Burkitt lymphoma and nasopharyngeal carcinoma. Cytomegalovirus (CMV) causes congenital infection and disease in transplant and HIV patients. HHV-6 causes roseola in infants, and HHV-8 is associated with Kaposi sarcoma.
Because these viruses encode their own DNA polymerase and, in some cases, a thymidine kinase, they are targets for antiviral therapy. Acyclovir and its relatives are activated by viral thymidine kinase and inhibit HSV and VZV replication, while ganciclovir, foscarnet, and cidofovir are used against CMV. Antivirals suppress replication and shorten outbreaks but do not eliminate latent virus.
Herpesviruses are heavily tested on USMLE Step 1, which emphasizes the latency site, clinical syndrome, and cancer associations of each virus. The PTCE also covers the antiviral drug classes used against herpesviruses, including acyclovir, valacyclovir, and ganciclovir.
Key takeaways
- Herpesviruses are enveloped double-stranded DNA viruses that establish lifelong latent infection with potential reactivation.
- HSV-1 and HSV-2 remain latent in sensory neurons, VZV in dorsal root ganglia, and EBV in B cells.
- EBV is linked to Burkitt lymphoma and nasopharyngeal carcinoma, and HHV-8 to Kaposi sarcoma.
- Acyclovir-class drugs require viral thymidine kinase for activation and treat HSV and VZV; ganciclovir targets CMV.
- USMLE Step 1 tests latency sites and disease associations, while the PTCE covers herpes antiviral medications.