There are nine herpesviruses known to infect humans, officially numbered HHV-1 through HHV-8 (with HHV-6 split into two distinct species, 6A and 6B). But the herpesvirus family is far larger than that. The International Committee on Taxonomy of Viruses recognizes 118 species across the full family, infecting everything from oysters to elephants. Most people asking this question, though, want to understand the ones that matter for human health.
The Eight Human Herpesviruses
Each human herpesvirus has both an official number and a more common name. They fall into three subfamilies based on which cells they prefer and how they behave once inside the body.
- HHV-1 (Herpes Simplex Virus 1): The main cause of oral cold sores. An estimated 3.8 billion people under 50, roughly 64% of the global population, carry it.
- HHV-2 (Herpes Simplex Virus 2): Primarily causes genital herpes. About 520 million people aged 15 to 49 worldwide (13%) are infected.
- HHV-3 (Varicella-Zoster Virus): Causes chickenpox on first infection and shingles when it reactivates later in life.
- HHV-4 (Epstein-Barr Virus): Best known for causing mono (infectious mononucleosis). Over 95% of adults worldwide carry it.
- HHV-5 (Cytomegalovirus): Usually causes no symptoms in healthy people. Over half of adults have been infected by age 40.
- HHV-6A and HHV-6B: Originally classified as one virus, now recognized as two separate species. HHV-6B is the cause of roseola, the common childhood illness with high fever and a rash. HHV-6A’s role in disease is less clear.
- HHV-7: Closely related to HHV-6 and also linked to roseola in some cases. Nearly everyone is infected during childhood.
- HHV-8 (Kaposi Sarcoma Herpesvirus): The least common of the group. It causes Kaposi sarcoma, a cancer that primarily affects people with weakened immune systems.
The Three Subfamilies
The human herpesviruses are grouped into three subfamilies, and the groupings tell you a lot about how each virus operates in your body.
Alphaherpesviruses (HHV-1, HHV-2, HHV-3)
These are the fast movers. They replicate quickly, tend to cause visible blisters or sores on the skin, and go dormant in nerve cells. That’s why cold sores reappear in the same spot on your lip and why shingles follows a nerve path across one side of your body. The virus never leaves those neurons. It simply goes quiet and can reactivate when your immune system is stressed or suppressed.
Betaherpesviruses (HHV-5, HHV-6A, HHV-6B, HHV-7)
These viruses replicate more slowly and tend to infect a narrower range of cells. Cytomegalovirus (HHV-5) is the most medically significant of this group. It rarely causes problems for healthy adults but can be dangerous for newborns, organ transplant recipients, and others with compromised immune systems. HHV-6B and HHV-7 infect almost everyone during early childhood, often so mildly that parents don’t realize it happened.
Gammaherpesviruses (HHV-4, HHV-8)
The two gammaherpesviruses stand out because they are both classified as class I carcinogens by the World Health Organization, meaning they definitively cause cancer in humans. Epstein-Barr virus is linked to several types of lymphoma and nasopharyngeal carcinoma. HHV-8 causes Kaposi sarcoma and is also associated with certain rare lymphomas. Each of these viruses is connected to roughly 1 to 2% of all human cancers. Both establish latency primarily in immune cells, particularly B cells, rather than in nerve cells like the alphaherpesviruses.
Why All Herpesviruses Are Lifelong Infections
The defining trait of every herpesvirus is latency. After the initial infection, the virus tucks its DNA into specific host cells and enters a dormant state where it produces little to no protein. In this state, the immune system largely can’t detect it. The virus persists for life, periodically reactivating to produce new copies of itself before going dormant again.
Where the virus hides depends on the subfamily. Alphaherpesviruses camp out in sensory nerve cells. Gammaherpesviruses settle into B cells, a type of white blood cell. Betaherpesviruses have more variable hiding spots, including immune cells and bone marrow progenitor cells. This strategy is remarkably effective: most adults carry several herpesviruses simultaneously without any symptoms at all.
Beyond the Human Eight
The full herpesvirus family contains 118 recognized species spread across three subfamilies and 17 genera. Nearly every animal group studied, from fish to birds to primates, has its own set of herpesviruses. These viruses are typically species-specific, meaning a herpesvirus adapted to one animal rarely jumps to another.
The notable exception is B virus, a herpesvirus carried by macaque monkeys. In macaques, it behaves much like a cold sore virus. In humans, it can cause severe brain inflammation that is often fatal without treatment. Transmission happens through bites, scratches, or contact with a monkey’s bodily fluids. Infections are extremely rare and essentially limited to people who work directly with macaques in laboratory or veterinary settings.
How Common Are These Infections?
If you’ve never been diagnosed with a herpesvirus, you almost certainly still carry at least one. The numbers make this clear: 64% of people under 50 have HSV-1, over 95% of adults carry Epstein-Barr virus, more than half of adults have cytomegalovirus by age 40, and nearly everyone picks up HHV-6B and HHV-7 in early childhood. Add it all up, and the average adult is carrying multiple herpesviruses at any given time. For the vast majority of people, these viruses cause no ongoing symptoms and require no treatment. The immune system keeps them in check, and the viruses persist quietly in their latent hideouts for decades.