- Herpes simplex virus (HSV) is a widespread, double-stranded DNA virus belonging to the Herpesviridae family, known for causing a range of infections in humans, from mild mucocutaneous lesions to severe systemic disease.
- There are two closely related types of HSV: HSV-1 and HSV-2. HSV-1 is typically associated with oral and facial infections, such as cold sores, while HSV-2 more commonly causes genital herpes. However, both types are capable of infecting either region, especially with changing patterns of sexual behavior.
- HSV is characterized by its ability to establish lifelong latency in the host’s sensory neurons following primary infection. After the initial exposure—often asymptomatic or presenting with flu-like symptoms and localized lesions—the virus travels along peripheral nerves to sensory ganglia (such as the trigeminal ganglion for HSV-1 and the sacral ganglion for HSV-2), where it remains dormant. Reactivation can occur periodically, triggered by stress, illness, immunosuppression, or UV exposure, leading to recurrent episodes of symptomatic or asymptomatic viral shedding and lesion formation.
- Transmission of HSV occurs primarily through direct contact with infected secretions, including saliva, genital fluids, or lesions. Oral HSV-1 is most commonly acquired in childhood, often through nonsexual contact, while HSV-2 is usually transmitted sexually and typically acquired during adolescence or adulthood. Vertical transmission from mother to infant can also occur, particularly during childbirth, and may result in neonatal herpes, a potentially life-threatening condition.
- Clinically, HSV infections manifest in a variety of ways. Oral herpes presents as clusters of painful blisters around the lips and mouth, while genital herpes involves painful ulcers or vesicles in the genital and anal regions, often accompanied by systemic symptoms during the first outbreak. In immunocompromised individuals, HSV can cause more severe disease, including herpes encephalitis, keratitis (eye infection), and widespread cutaneous lesions. HSV encephalitis, primarily caused by HSV-1, is a medical emergency associated with high mortality and long-term neurological damage if not promptly treated.
- Diagnosis of HSV infection is based on clinical presentation and confirmed by laboratory tests such as PCR (polymerase chain reaction), viral culture, or serology. PCR is the most sensitive and specific method, especially for detecting viral DNA in cerebrospinal fluid in cases of suspected herpes encephalitis.
- Treatment for HSV involves antiviral medications, primarily acyclovir, valacyclovir, and famciclovir. These drugs do not cure the infection but can shorten the duration of symptoms, promote healing, and reduce viral shedding and the risk of transmission. Long-term suppressive therapy may be used in individuals with frequent recurrences or in those with immunosuppression. Research is ongoing to develop effective vaccines and novel therapeutics to better control HSV infections and prevent reactivation.
