There are eight herpesviruses that infect humans, not just the two most people think of. They range from the cold sore virus to the cause of chickenpox, mono, and even certain cancers. All eight share one defining trait: once you’re infected, the virus stays in your body for life, hiding in a dormant state and occasionally reactivating.
HSV-1: The Cold Sore Virus
Herpes simplex virus type 1 is the most common herpesvirus on the planet. An estimated 3.8 billion people under age 50, roughly 64% of the global population, carry it. Most people pick it up in childhood through nonsexual contact like a kiss from a family member or sharing utensils. It typically causes oral herpes: cold sores or fever blisters around the mouth and lips.
HSV-1 can also cause genital herpes, usually through oral sex. About 376 million people aged 15 to 49 have genital HSV-1 infections. Many carriers never develop visible sores and don’t realize they’re infected, but they can still pass the virus to others during periods of “viral shedding,” when the virus is active on the skin surface without causing symptoms.
Beyond cold sores, HSV-1 is responsible for herpes keratitis (an eye infection that can damage the cornea), herpetic whitlow (painful sores on the fingers), and in rare cases, encephalitis, a serious brain infection.
HSV-2: The Primary Cause of Genital Herpes
Herpes simplex virus type 2 is spread almost exclusively through sexual contact and is the leading cause of genital herpes worldwide, affecting roughly 520 million people aged 15 to 49. Of those, about 205 million experienced at least one symptomatic outbreak in 2020.
Symptoms look similar to HSV-1 genital infections: painful blisters or ulcers in the genital or anal area, sometimes accompanied by flu-like symptoms during the first outbreak. The key difference is recurrence. HSV-2 genital infections tend to reactivate more frequently than genital HSV-1 infections, sometimes several times a year, though outbreaks typically become less severe and less frequent over time.
HSV-2 can also cause oral herpes, though this is less common. Like HSV-1, it hides in nerve cells near the spine after the initial infection and reactivates periodically. Antiviral medications can reduce outbreak frequency and lower the risk of transmission but don’t eliminate the virus.
Varicella-Zoster Virus (HHV-3)
This is the virus behind two distinct illnesses: chickenpox in childhood and shingles in adulthood. Nearly everyone who grew up before the chickenpox vaccine became available carries this virus. After a case of chickenpox resolves, the virus retreats into nerve cells along the spine, where it maintains its genetic material with almost no activity, producing very little viral protein.
Decades later, when the immune system weakens due to aging, stress, illness, or immunosuppressive medications, the virus can reactivate as shingles. Shingles produces a painful, blistering rash that typically appears in a band on one side of the body, following the path of the nerve where the virus was hiding. A vaccine is now available for adults over 50 to reduce the risk of shingles and its most debilitating complication, prolonged nerve pain that can last months after the rash clears.
Epstein-Barr Virus (HHV-4)
Epstein-Barr virus is best known as the cause of infectious mononucleosis, or “mono,” the illness sometimes called the kissing disease. It spreads through saliva and is extremely common. Most people are infected by adulthood, often without realizing it. When symptoms do appear, usually in teenagers or young adults, they include extreme fatigue, sore throat, fever, and swollen lymph nodes that can last weeks.
What makes EBV notable among the herpesviruses is its link to several cancers. It plays a role in nasopharyngeal carcinoma (a cancer of the upper throat), Burkitt lymphoma, Hodgkin lymphoma, and certain stomach cancers. These cancers are rare relative to how many people carry the virus, but the connection is well established. EBV has also been identified as a significant risk factor for multiple sclerosis, though the exact mechanism is still being studied. In people with weakened immune systems, the virus can drive uncontrolled growth of white blood cells, a condition called lymphoproliferative syndrome.
Cytomegalovirus (HHV-5)
Cytomegalovirus, or CMV, is another herpesvirus that most people carry without ever knowing it. In healthy adults, it rarely causes noticeable illness. When it does produce symptoms, they mimic mono: fever, sore throat, fatigue, and swollen glands. Occasionally it causes liver inflammation.
CMV becomes dangerous in two situations. For people with weakened immune systems, such as organ transplant recipients or those with advanced HIV, CMV can cause serious infections of the eyes, lungs, liver, esophagus, stomach, and intestines. For pregnant women, a first-time CMV infection can pass to the developing baby. About 1 in 5 babies born with congenital CMV infection will have birth defects or long-term health problems. Hearing loss is the most common, sometimes appearing at birth and sometimes developing later in childhood.
HHV-6 and HHV-7: The Roseola Viruses
These two closely related viruses are responsible for roseola infantum, one of the most common childhood illnesses. Roseola primarily affects children between 6 months and 3 years old. The pattern is distinctive: a high fever (often 103 to 105°F) appears suddenly and lasts 3 to 5 days with no other obvious symptoms. When the fever drops, usually abruptly on the fourth day, a pinkish rash appears on the chest and abdomen, sometimes spreading to the face and limbs. The rash lasts anywhere from a few hours to two days and can be so mild it goes unnoticed.
HHV-6 (specifically the 6B subtype) causes most cases of roseola, while HHV-7 accounts for a smaller share. By the time children reach school age, nearly all have been infected with both viruses. In rare cases, HHV-6 can cause encephalitis or contribute to ear infections with fever. After the initial infection, both viruses remain dormant and occasionally reactivate, though this is typically only a concern for immunocompromised individuals.
HHV-8: Kaposi Sarcoma Herpesvirus
The eighth human herpesvirus is unique in that it doesn’t cause an obvious acute illness. Instead, it’s known for its role in Kaposi sarcoma, a cancer that forms in the lining of blood and lymph vessels and appears as purple or dark lesions on the skin, mouth, or internal organs. HHV-8 also plays a role in primary effusion lymphoma and a condition called multicentric Castleman disease, both of which involve abnormal growth of immune cells.
Kaposi sarcoma was one of the earliest recognized signs of the AIDS epidemic in the 1980s, and HHV-8 remains most dangerous in people with HIV or other causes of severe immune suppression. In people with healthy immune systems, HHV-8 infection rarely causes problems. The virus is less common than the other human herpesviruses, with prevalence varying widely by region.
How Herpesviruses Are Tested
If you have visible sores, the most reliable test is a PCR (polymerase chain reaction) test, which detects viral DNA directly from a swab of the sore. PCR is more sensitive than the older method of viral culture and increases detection rates by about 24%. Viral culture works best when a blister is fresh, ideally less than 24 hours old, and is less reliable for recurrent outbreaks than for first episodes.
Blood tests can detect antibodies your immune system has made against the virus, confirming past infection. For HSV specifically, a standard antibody test can’t easily distinguish between type 1 and type 2 because the two viruses are so similar. A specialized test targeting a protein called glycoprotein G is needed to tell them apart. For suspected brain infections caused by herpes, PCR testing of spinal fluid is the gold standard and is as sensitive as a brain biopsy while being far less invasive.
Why All Eight Stay for Life
Every herpesvirus uses the same core survival strategy. After the initial infection, the virus inserts its genetic material into long-lived cells, often nerve cells or immune cells, and goes quiet. It produces just enough molecular activity to maintain itself without triggering an immune response. When conditions shift (stress, illness, immune suppression, aging), the virus can reactivate, producing new copies of itself and sometimes causing symptoms again. This cycle of latency and reactivation is what makes herpesviruses impossible to fully clear from the body with current treatments. Antiviral medications target the virus during its active phases but can’t reach it while it’s dormant inside cells.