There are eight types of herpesvirus that infect humans, numbered Human Herpesvirus 1 through 8 (HHV-1 through HHV-8). Most people only think of cold sores or genital herpes when they hear “herpes,” but the herpesvirus family also includes the viruses behind chickenpox, mono, and several other common infections. 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.
The Three Subfamilies
Scientists group the eight human herpesviruses into three subfamilies based on how they behave in the body. The alpha herpesviruses (HHV-1, HHV-2, and HHV-3) hide in nerve cells during their dormant phase. The beta herpesviruses (HHV-5, HHV-6, and HHV-7) tend to infect immune cells and can cause cells to swell dramatically. The gamma herpesviruses (HHV-4 and HHV-8) target a type of white blood cell called B lymphocytes and are linked to certain cancers.
Each virus spreads differently, causes different symptoms, and hides in different tissues. Here’s what each one actually does.
HHV-1: Oral Herpes (HSV-1)
Herpes simplex virus type 1 is the most widespread of the group. It mostly spreads through oral contact, causing cold sores or fever blisters in and around the mouth. It can also cause genital herpes when transmitted through oral-genital contact, though that’s less common. The virus spreads through sores, saliva, or skin surfaces around the mouth, and it can be transmitted even when the skin looks normal. The greatest risk of passing it on is when active sores are present.
After the initial infection, HSV-1 retreats to nerve clusters near the base of the skull called the trigeminal ganglia. It stays dormant there, potentially reactivating during periods of stress, illness, or sun exposure to cause new outbreaks.
HHV-2: Genital Herpes (HSV-2)
Herpes simplex virus type 2 spreads through sexual contact and causes genital herpes. It transmits through contact with genital or anal skin, sores, or fluids, and notably, it can spread even when no symptoms are visible. Many people with HSV-2 don’t know they carry it because outbreaks can be mild or completely absent.
HSV-2 establishes latency in the sacral dorsal root ganglia, a nerve cluster near the base of the spine. From there it can reactivate periodically, though outbreaks typically become less frequent over time.
HHV-3: Chickenpox and Shingles
Varicella-zoster virus causes two distinct diseases at different stages of life. The first infection, usually in childhood, produces chickenpox: an itchy, blistering rash with fever. After recovery, the virus goes dormant in sensory nerve cells throughout the body. Decades later, it can reactivate as shingles, a painful rash that typically appears in a band on one side of the torso or face. The risk of shingles rises significantly after age 50, which is why a shingles vaccine is recommended for older adults.
HHV-4: Epstein-Barr Virus
Epstein-Barr virus (EBV) is best known for causing mononucleosis, often called “mono” or the “kissing disease.” It spreads primarily through saliva. Most people get infected at some point in their lives, often during childhood when symptoms are mild or absent. When teenagers or young adults catch it for the first time, they’re more likely to develop the classic mono symptoms: extreme fatigue, sore throat, swollen lymph nodes, and fever that can last weeks.
EBV infects B lymphocytes, a key part of the immune system, and can essentially make those cells immortal in lab settings. It hides in B cells for life and has been linked to several types of cancer, including certain lymphomas and nasopharyngeal cancer. Researchers have also been investigating connections between EBV and autoimmune conditions like multiple sclerosis.
HHV-5: Cytomegalovirus (CMV)
Cytomegalovirus is remarkably common and almost always harmless in healthy people. Most who catch it never notice any symptoms at all. Some develop a condition resembling mono, with prolonged fever and liver inflammation. Like other herpesviruses, CMV stays in the body permanently and rarely causes problems unless the immune system is significantly weakened by medication or disease.
Where CMV becomes genuinely dangerous is during pregnancy. When a mother passes the virus to her baby before birth (congenital CMV), about 10% of those infants show signs at birth, including jaundice, an abnormally small head, an enlarged liver and spleen, or seizures. Of the babies born with visible signs, 40 to 60% develop long-term problems like hearing loss, developmental delays, or vision loss. Congenital CMV is one of the leading infectious causes of birth defects.
HHV-6: Roseola (Sixth Disease)
Human herpesvirus 6 comes in two variants, HHV-6A and HHV-6B. HHV-6B is the strain behind roseola, one of the most common childhood illnesses. It typically strikes between 6 months and 2 years of age. The hallmark pattern is a sudden high fever, often above 103°F (39.4°C), lasting 3 to 5 days. Once the fever breaks, a flat, pinkish rash appears on the chest, back, and belly before spreading to the neck and arms. The rash itself isn’t itchy or painful and fades within hours to days.
Other symptoms can include irritability, mild diarrhea, decreased appetite, swollen eyelids, and swollen lymph nodes. By adulthood, the vast majority of people have been infected. The virus infects T lymphocytes (immune cells) and remains dormant afterward. HHV-6A is less well understood but has been found in some neurological conditions.
HHV-7: The Quiet Cousin
Human herpesvirus 7 is closely related to HHV-6 and also infects T lymphocytes. Nearly everyone gets infected during early childhood, usually without any noticeable illness. HHV-7 can occasionally cause a second bout of roseola-like symptoms or mild fever in young children. It’s the least studied and least clinically significant of the eight human herpesviruses. After infection, it persists mainly in immune cells and has been detected in tonsillar and adenoidal tissue.
HHV-8: Kaposi’s Sarcoma Virus
Human herpesvirus 8, also called Kaposi’s sarcoma-associated herpesvirus (KSHV), is the rarest of the eight types in most populations. It’s primarily known for causing Kaposi’s sarcoma, a cancer that forms dark, purplish lesions in blood vessel walls and on the skin. This cancer gained attention during the early AIDS epidemic because it appeared frequently in people with severely weakened immune systems. HHV-8 also causes certain rare lymphomas. In people with healthy immune systems, the virus typically causes no symptoms at all.
One Thing They All Share: Lifelong Latency
The single trait that unites all eight human herpesviruses is their ability to establish lifelong latency. After the initial infection clears, the virus doesn’t leave your body. Instead, it retreats into specific cells, shuts down most of its activity, and essentially hides from your immune system. The alpha herpesviruses (HSV-1, HSV-2, and varicella-zoster) prefer nerve cells. The beta and gamma herpesviruses tend to hide in immune cells, though researchers have also found dormant herpesvirus DNA in tonsils, blood vessel walls, and connective tissue cells called fibroblasts.
Reactivation happens when the immune system is stressed or suppressed. For HSV-1, that might mean a cold sore during a stressful week. For varicella-zoster, it could mean shingles decades after a childhood case of chickenpox. For CMV or HHV-8, reactivation typically only causes disease in people whose immune systems are compromised. The pattern is consistent: the virus wakes up, reproduces briefly, and your immune system pushes it back into dormancy.
A Ninth Type? Not Yet
No ninth human herpesvirus has been officially recognized. The count has held at eight since HHV-8 was identified in the mid-1990s. There are, however, herpesviruses in other animals that can occasionally jump to humans. The most notable is B virus, carried by macaque monkeys. Human B virus infection is extremely rare, but when it does occur, it can cause severe brain inflammation and is often fatal without immediate treatment. People at risk are almost exclusively those who work directly with macaques in research or veterinary settings.