Eight types of herpesvirus infect humans, numbered Human Herpesvirus 1 through 8 (HHV-1 to HHV-8). Most people will encounter several of them during their lifetime, often without realizing it. While “herpes” typically brings cold sores or genital sores to mind, the herpes family also includes the viruses behind chickenpox, mono, and certain cancers.
The Eight Human Herpesviruses
Each of the eight types has a formal HHV number and a more familiar common name:
- HHV-1: Herpes simplex virus type 1 (HSV-1), the main cause of oral cold sores
- HHV-2: Herpes simplex virus type 2 (HSV-2), the main cause of genital herpes
- HHV-3: Varicella-zoster virus (VZV), the cause of chickenpox and shingles
- HHV-4: Epstein-Barr virus (EBV), best known for causing mono
- HHV-5: Cytomegalovirus (CMV), usually harmless in healthy adults but dangerous for newborns and people with weakened immune systems
- HHV-6A and HHV-6B: The primary cause of roseola in infants
- HHV-7: Closely related to HHV-6, also linked to roseola
- HHV-8: Kaposi sarcoma-associated herpesvirus (KSHV), linked to certain cancers
All eight share one defining trait: once you’re infected, the virus stays in your body for life. It can go dormant, hiding inside cells without producing symptoms, and then reactivate later under certain conditions.
How Herpesviruses Stay in Your Body
After an initial infection, herpesviruses don’t get cleared by the immune system the way a cold virus does. Instead, viral DNA persists inside specific cells, often nerve cells, in a dormant state where no new virus is produced. Your immune system can’t detect the virus during this quiet phase because the genes that would signal its presence are switched off.
Reactivation can happen spontaneously or in response to triggers like fever, UV light exposure, physical stress, or dental work. With HSV-1 and HSV-2, reactivation doesn’t always mean visible sores. Research shows that HSV-1 sheds from the body roughly 35% of the time and HSV-2 about 15% of the time, often with no noticeable symptoms.
HSV-1 and HSV-2: Cold Sores and Genital Herpes
These are the two viruses people usually mean when they say “herpes.” HSV-1 traditionally causes oral cold sores, while HSV-2 causes genital outbreaks, but either type can infect either location. According to the WHO, around 846 million people aged 15 to 49 are living with genital herpes infections globally, which works out to more than 1 in 5 adults. About 520 million of those cases are caused by HSV-2, while roughly 376 million are genital infections caused by HSV-1. It’s possible to carry both types simultaneously.
An estimated 42 million people acquire a new genital herpes infection every year. Despite how common it is, many carriers never have noticeable symptoms. More than 200 million people experienced at least one symptomatic episode in 2020, which means a significant portion of those infected remain unaware.
Testing for HSV has real limitations. Swab tests taken directly from an active blister or sore are the most accurate. Blood tests, which look for antibodies, can take up to 16 weeks after exposure to detect the infection. The CDC notes that the chance of a false positive is much higher with herpes blood tests than with tests for infections like chlamydia or gonorrhea, particularly in people at low risk.
VZV: Chickenpox and Shingles
HHV-3, or varicella-zoster virus, causes chickenpox during the initial infection, usually in childhood. After the rash clears, the virus retreats into nerve cells near the spine and skull. Decades later, it can reactivate as shingles, a painful blistering rash that typically appears in a band on one side of the body. The risk of shingles rises with age and anything that weakens the immune system.
Epstein-Barr Virus: Mono and Beyond
HHV-4, the Epstein-Barr virus, is best known for causing infectious mononucleosis, or “mono.” Symptoms include extreme fatigue, sore throat, fever, and swollen lymph nodes, and it spreads through saliva. Most people are infected by adulthood, though many never develop obvious symptoms. EBV has also been linked to certain lymphomas and nasopharyngeal cancers, and growing evidence connects it to the development of multiple sclerosis.
CMV: Usually Silent, Sometimes Serious
Cytomegalovirus (HHV-5) spreads through body fluids including saliva, urine, blood, breast milk, and semen. Most healthy adults who catch it experience nothing, or at most mild fatigue, fever, and sore throat that resembles mono. The virus becomes genuinely dangerous in two situations.
For babies infected before or during birth (congenital CMV), the consequences can be severe. Most appear healthy at first, but some are born with jaundice, low birth weight, seizures, or eye damage. Even babies who seem fine at birth can develop hearing loss or developmental delays months or years later.
For people with weakened immune systems, such as organ transplant recipients or those with advanced HIV, CMV can cause serious inflammation in the eyes, lungs, liver, brain, and digestive tract.
HHV-6 and HHV-7: Roseola in Infants
These two closely related viruses are so common that nearly all children are infected by age two. HHV-6B is the primary cause of roseola (sometimes called “sixth disease”), a childhood illness that starts with a sudden high fever, often reaching 103 to 105°F, lasting about three to four days. After the fever breaks, a pinkish rash may appear and last two to four days. Some children also develop vomiting or diarrhea before the rash shows up. The incubation period is 5 to 15 days after exposure.
HHV-7 can cause a similar illness. Both viruses are generally mild and resolve on their own, though the high fever can occasionally trigger febrile seizures in young children.
HHV-8: The Cancer-Linked Herpesvirus
HHV-8 is the least common of the eight and the most closely tied to cancer. It’s the cause of Kaposi sarcoma, a cancer that produces dark skin lesions and can also affect internal organs. Kaposi sarcoma became widely recognized during the early HIV/AIDS epidemic because HHV-8 primarily causes disease in people with severely weakened immune systems. HHV-8 is also associated with certain rare lymphomas. In people with healthy immune systems, the virus typically causes no symptoms at all.
Can You Catch Herpes From Animals?
The eight human herpesviruses spread exclusively between people, but there is one animal herpesvirus that can cross into humans. B virus, carried by macaque monkeys, is extremely rare in people but potentially fatal. Infection happens through bites, scratches, or contact with a monkey’s body fluids. Without immediate treatment, B virus can cause severe brain inflammation, and death can occur within one day to three weeks after symptoms appear. This is essentially only a risk for laboratory workers, veterinarians, or others who handle macaques directly.