Herpes Simplex Virus (HSV) is a common infection with two distinct types, HSV-1 and HSV-2. Both viruses, once acquired, remain dormant within the body’s nerve cells for life. The term “herpes” refers to an infection caused by one of these two strains, which primarily differ in their preferred site of latency and their tendency to reactivate.
Distinct Differences in Transmission and Site of Infection
HSV-1 has traditionally been associated with oral infections, presenting as cold sores around the mouth. Transmission typically occurs through non-sexual contact, such as kissing or sharing utensils, leading to latency in the trigeminal ganglia near the skull. However, HSV-1 is now an increasingly common cause of new genital herpes infections. In contrast, HSV-2 is primarily transmitted through sexual contact and is the most frequent cause of genital herpes. After initial infection, HSV-2 establishes latency in the sacral ganglia. This difference in nerve location is a biological factor contributing to the varying clinical patterns observed between the two types.
Viral shedding is the period when the virus is active on the skin surface and transmissible, often occurring without visible symptoms. Genital HSV-2 has high and persistent rates of asymptomatic shedding, occurring on about 17% to 34% of days even years after infection. Genital HSV-1 shedding is substantially less frequent and tends to decline rapidly; one study found shedding occurred on only about 7% of days one year after the first episode. This lower rate makes genital HSV-1 less transmissible over time compared to HSV-2.
Comparing Acute Symptom Severity and Recurrence Rates
The primary outbreak for both HSV-1 and HSV-2 can be severe, often involving painful blisters and systemic symptoms like fever, headache, and swollen lymph nodes. Primary genital HSV-2 infections are often reported to be more severe and prolonged than primary genital HSV-1 infections. These first symptomatic episodes are generally the most uncomfortable phase of the infection.
The most significant difference lies in their recurrence rates following the primary infection. HSV-2 has a notably higher tendency to reactivate and cause recurrent outbreaks than genital HSV-1. Individuals with untreated genital HSV-2 infection typically experience a median of four to six recurrences in the first year alone. Recurrences of genital HSV-1 are significantly less frequent, with a median rate of approximately one outbreak during the first year. For oral HSV-1 (cold sores), recurrences are common but generally milder and shorter in duration than genital outbreaks.
Potential Long-Term Health Risks and Complications
Both types of HSV carry the risk of long-term health complications. Neonatal herpes is one of the most severe complications, transmitted to an infant during childbirth. The prognosis for neonatal infection is worse when caused by HSV-2, which is responsible for the majority of these cases, compared to HSV-1.
Infections of the central nervous system (CNS) are also possible for both viruses. HSV-1 is the most common cause of sporadic fatal encephalitis, a life-threatening inflammation of the brain. While rare, HSV-1 CNS infection is associated with a higher short-term mortality rate and a greater long-term risk of neurological disability than HSV-2 CNS infection.
HSV-2 is the most frequent cause of recurrent viral meningitis, known as Mollaret’s meningitis. Separately, HSV-1 is the primary cause of ocular herpes, or keratitis, which can lead to corneal scarring and vision loss if left untreated. Furthermore, the psychosocial impact of a genital herpes diagnosis, particularly HSV-2, can be substantial due to the stigma associated with sexually transmitted infections.
Diagnosis and Management
Diagnosing an HSV infection begins with a physical examination of any visible sores or blisters. To confirm the diagnosis and determine the specific viral type, healthcare providers typically take a sample from an active sore for viral culture or, more commonly, a nucleic acid amplification test (NAAT or PCR). These tests are necessary because the appearance of sores from HSV-1 and HSV-2 can be identical.
If no active lesions are present, a blood test can detect antibodies against the virus, indicating a past infection. It is important to request a type-specific serological test, as many standard screenings for sexually transmitted infections may not include HSV, and non-specific tests cannot differentiate between HSV-1 and HSV-2 antibodies.
While there is no cure for either virus, both are managed effectively with antiviral medications such as acyclovir, valacyclovir, or famciclovir. These drugs can be used as episodic therapy to shorten the duration and severity of an outbreak when symptoms first appear. For individuals with frequent recurrences, suppressive therapy involves taking a daily dose of antiviral medication, a strategy most often recommended for HSV-2 due to its higher recurrence rate, which significantly reduces the frequency of outbreaks and lowers the risk of transmission.