Herpes simplex virus 1 (HSV-1) is a member of the human alphaherpesviruses and a major cause of oral herpes. It contains a large double-stranded DNA genome enclosed in an icosahedral capsid and lipid envelope. The virus infects epithelial cells, producing vesicular lesions in the mouth or face, and then establishes lifelong latency in sensory neurons.
Pathogenesis, prevalence and transmission
HSV-1 replicates in mucocutaneous tissues after entering through breaches in the skin or mucosa. Viral particles travel via retrograde axonal transport to sensory ganglia, where the genome persists as an episome and remains dormant until reactivation. During latency the virus expresses only a limited set of transcripts; during reactivation it produces new virions that travel along axons to the skin, causing recurrent lesions. Estimates suggest that more than half of the world’s population carries HSV-1, and infection is often acquired in childhood through non-sexual contact. Transmission occurs via saliva, contact with contaminated secretions or lesions and, less commonly, through oral-genital contact leading to genital infection. Most infections are asymptomatic, but symptomatic cases may involve cold sores, gingivostomatitis or keratitis. Periodic shedding without visible lesions contributes to viral spread. Antiviral agents such as acyclovir and valaciclovir inhibit viral DNA replication and are used to treat severe or recurrent outbreaks, though they do not eliminate latent virus. Prevention focuses on avoiding direct contact with active lesions and practising good hygiene.
Clinical examples and notable facts
Cold sores at the lip border are the classic presentation of HSV-1 infection. Primary infections in children can manifest as painful gingivostomatitis with fever and malaise. The virus can infect the cornea, leading to herpes keratitis, a major cause of corneal blindness worldwide. Rarely, HSV-1 spreads to the brain and causes herpes simplex encephalitis, a severe but treatable form of viral encephalitis. Reactivation is often triggered by stress, fever, ultraviolet light or immunosuppression. Although HSV-1 traditionally causes oral disease, it is now a significant cause of genital herpes in many countries due to changing sexual practices. Infected individuals may shed virus without symptoms, underscoring the importance of awareness and testing. A lifelong neurotropic infection with HSV-1 usually follows a pattern of primary infection, latency and periodic reactivation. While most carriers remain asymptomatic, the virus can cause recurrent mucocutaneous lesions and, in rare cases, serious ocular or central nervous system disease. Effective antiviral drugs can control outbreaks, but there is currently no vaccine to prevent acquisition of HSV-1. Related Terms: Herpes Simplex Virus 2 (HSV-2), Varicella-Zoster Virus (VZV), Epstein-Barr Virus (EBV), Cytomegalovirus (CMV), Human Herpesvirus 6