The herpes simplex virus (HSV) is a highly prevalent infection worldwide, categorized into two main types. HSV-1 is most commonly associated with oral herpes (cold sores), although it is increasingly responsible for genital infections. HSV-2 is the primary cause of genital herpes. A significant challenge in managing the spread of this virus is the large number of people who carry the infection without ever knowing their status. This widespread unawareness is a primary factor fueling transmission, making the virus far more common than many people realize.
The Global Scale of Undiagnosed Herpes
The number of individuals living with herpes is substantial globally, with billions infected with one or both types of the virus. Worldwide, an estimated 3.8 billion people under 50 carry HSV-1 (about 64% of that population). HSV-2 is less widespread but still affects an estimated 520 million people aged 15 to 49 globally, or about 13% of that age group.
The prevalence of undiagnosed cases is particularly pronounced for genital herpes caused by HSV-2. In the United States, about one in six people aged 14 to 49 is estimated to be infected with HSV-2. Studies indicate that as many as 75% to 90% of these infected individuals are unaware they carry the virus. This means the vast majority of people with genital herpes have never received an official diagnosis.
While HSV-1 infection rates are significantly higher globally, the rate of unawareness is still the norm, as most HSV infections are entirely asymptomatic or unrecognized. The percentage of undiagnosed cases is often highlighted for HSV-2 because it is the primary cause of recurrent genital disease. The high fraction of people unaware of their HSV-2 status underscores how silently the virus circulates within a population.
Clinical Reasons for Lack of Diagnosis
The primary factor contributing to this widespread unawareness is the biological nature of the virus itself, which often fails to produce noticeable symptoms. For most infected individuals, the virus establishes a latent infection in the nerve cells without ever causing a recognizable outbreak. This asymptomatic nature means that a person can carry the virus for decades without any indication of its presence.
When symptoms do occur, they are often mild and confused with other common conditions, referred to as subclinical symptoms. These atypical presentations might be mistaken for:
- Minor skin irritations
- Friction burns
- Acne
- Jock itch
Because the symptoms are brief or subtle, they are not recognized as herpes, the individual does not seek testing, and the infection remains undiagnosed.
The virus can be actively shed from the skin or mucosal surfaces even when no lesions or symptoms are visible. This process, known as asymptomatic viral shedding, is the biological mechanism of transmission. People shed infectious virus particles without knowing, directly linking the lack of symptoms to the continuing spread of the infection.
Transmission Risks Associated with Unawareness
The large population of undiagnosed carriers represents the most significant reservoir for new infections, as transmission most often occurs from individuals who are unaware they harbor the virus. Asymptomatic shedding, where the virus is active on the skin surface without causing symptoms, is the primary route of transmission to sexual partners. This shedding occurs a measurable percentage of days, even in individuals who have never had a recognized outbreak.
Silent transmission poses a challenge because people who do not know they are infected cannot take precautions to prevent passing the virus to others. While the risk of transmission is highest during an active outbreak, asymptomatic shedding is frequent, meaning the risk is always present. The unawareness of one partner can lead to the infection of another, perpetuating the cycle.
A particularly high-risk scenario is vertical transmission from a mother to her infant during childbirth. Most cases of neonatal herpes, which can cause severe neurological damage or death, occur when the mother has no known history of genital herpes. The highest risk of transmission (potentially 33% or more) is associated with a woman acquiring a primary herpes infection late in pregnancy, often without realizing it.
Testing Options for Asymptomatic Individuals
Since the vast majority of people who have herpes are unaware of their status, diagnosis in the absence of symptoms relies entirely on laboratory testing. The preferred method for diagnosing a past or asymptomatic infection is a type-specific blood test, which detects the body’s immune response to the virus. These tests specifically look for the presence of antibodies, which are proteins produced by the immune system to fight the virus.
The most reliable of these blood tests detects immunoglobulin G (IgG) antibodies. IgG antibodies remain in the bloodstream indefinitely after an infection, confirming a past exposure to either HSV-1 or HSV-2, even years later. The test works by identifying antibodies specific to viral proteins, such as glycoprotein G-1 for HSV-1 and glycoprotein G-2 for HSV-2.
Viral culture or Polymerase Chain Reaction (PCR) tests require an active lesion or sore to swab and are therefore not useful for asymptomatic people. Healthcare providers often recommend type-specific IgG testing for individuals who have a partner diagnosed with herpes or for those seeking a complete sexually transmitted infection screening. Because the antibodies may take up to 12 to 16 weeks to reach detectable levels after initial infection, testing too early can result in a false negative.