Eight types of herpesvirus infect humans. They are numbered HHV-1 through HHV-8, and while most people associate “herpes” only with cold sores or genital sores, the family is far broader. It includes the viruses behind chickenpox, mononucleosis, a common infant rash, and several cancers. Every one of these eight viruses shares a defining trait: once you’re infected, the virus stays in your body for life.
Why All Herpesviruses Stay for Life
After the initial infection clears, every herpesvirus retreats into specific cells and goes dormant. The virus essentially shuts down its active machinery and hides, undetected by your immune system. It can stay quiet for years or decades, then reactivate when conditions shift. The triggers vary by virus type but commonly include physical or emotional stress, fever, illness, immune suppression, hormonal changes, and even UV exposure from sunlight.
Reactivation doesn’t always cause symptoms. Sometimes the virus becomes active, sheds briefly, and goes dormant again without you ever noticing. Other times it produces a full flare, like a cold sore or a shingles rash. This cycle of dormancy and reactivation is what makes herpesviruses impossible to fully eliminate from the body once you’ve been infected.
Types 1 and 2: Herpes Simplex
These are the two viruses most people think of when they hear “herpes.” HSV-1 primarily causes oral herpes (cold sores around the mouth), while HSV-2 primarily causes genital herpes. But the distinction isn’t absolute. HSV-1 can spread to the genitals through oral sex, and it now accounts for a growing share of genital herpes cases.
HSV-1 spreads mainly through contact with sores, saliva, or skin around the mouth. HSV-2 spreads through sexual contact with genital or anal skin, sores, or fluids. Both can transmit even when no visible sores are present, during periods of invisible viral shedding.
The numbers are staggering. According to WHO estimates from 2020, about 846 million people between 15 and 49 have a genital herpes infection, which is more than one in five adults worldwide. Of those, 520 million have genital HSV-2 and roughly 376 million have genital HSV-1. It’s possible to carry both types at the same time, and an estimated 50 million people do.
Both viruses hide in nerve clusters near the spine after initial infection. Reactivation travels back along the nerves to the skin, which is why outbreaks tend to recur in the same general area. Triggers include stress, illness, fatigue, and sun exposure. Outbreaks typically become less frequent over time.
Type 3: Varicella-Zoster (Chickenpox and Shingles)
This is the virus behind two distinct illnesses at different stages of life. The first infection, usually in childhood, causes chickenpox. After recovery, the virus goes dormant in sensory nerve clusters along the spine and skull. Most adults worldwide carry latent varicella-zoster in these nerve cells.
Decades later, the virus can reactivate as shingles: a painful, blistering rash that typically appears in a band on one side of the body. Shingles becomes more common with age because the immune system’s ability to keep the virus suppressed gradually weakens. Some people develop lingering nerve pain after the rash heals, a condition that can persist for months or longer. Vaccines exist for both chickenpox (given in childhood) and shingles (recommended for adults over 50).
Type 4: Epstein-Barr Virus
Epstein-Barr virus (EBV) is the most common cause of infectious mononucleosis, the illness often called “mono.” It’s especially common among teenagers and young adults, spreading through saliva, which is why it picked up the nickname “the kissing disease.” Symptoms include extreme fatigue, sore throat, swollen lymph nodes, and fever that can last weeks.
Most people are infected with EBV at some point in their lives, often in childhood, when it typically causes no noticeable symptoms at all. The virus hides in immune cells called B cells after infection. In rare cases, EBV is linked to certain cancers, including some types of lymphoma and nasopharyngeal cancer. Reactivation can be triggered by immune suppression, certain medications like chemotherapy, or conditions that stimulate the B cells where the virus hides.
Type 5: Cytomegalovirus
Cytomegalovirus (CMV) is extremely common. Most healthy adults who catch it never realize it, though some develop symptoms resembling mono. The virus becomes a serious concern in two specific situations: pregnancy and immune suppression.
CMV is the most common infectious cause of birth defects in the United States. About 1 in 200 babies is born with a congenital CMV infection. Of those, roughly 1 in 5 will develop birth defects or long-term health problems. The most frequent complication is hearing loss, which can appear at birth or develop later in childhood. Babies born with CMV can also have problems affecting the brain, liver, spleen, lungs, and growth.
For people with weakened immune systems, such as organ transplant recipients or those with advanced HIV, CMV can cause serious illness affecting the eyes, lungs, liver, esophagus, stomach, and intestines. CMV reactivation is particularly common when the immune system is suppressed and inflammatory signals push the virus’s host cells to mature, essentially waking the virus up in the process.
Types 6 and 7: The Roseola Viruses
HHV-6 and HHV-7 cause roseola, a very common childhood illness that most children catch before age two. HHV-6B is the primary culprit, with HHV-7 responsible for a smaller share of cases. (A related variant, HHV-6A, exists but isn’t clearly linked to clinical disease.)
Roseola follows a distinctive pattern. It begins with a sudden high fever, often between 103°F and 105°F, lasting three to five days. Despite the alarming temperature, most children stay alert and active, though febrile seizures can occur. When the fever drops, usually around the fourth day, a pink rash appears on the chest and abdomen and sometimes the face and limbs. The rash lasts anywhere from a few hours to two days. In about 70% of HHV-6 infections, the classic rash never appears at all, meaning many parents never realize their child had roseola.
Type 8: Kaposi Sarcoma Herpesvirus
HHV-8, also called Kaposi sarcoma-associated herpesvirus, is the least common of the eight and the most closely tied to cancer. It causes all forms 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 it was one of the first visible signs of advanced immune suppression.
Beyond Kaposi sarcoma, HHV-8 is associated with primary effusion lymphoma and a condition called multicentric Castleman’s disease, both of which involve abnormal growth of immune cells. These conditions occur almost exclusively in people with compromised immune systems. In people with healthy immune function, HHV-8 infection rarely causes noticeable disease.
Testing for Herpes Simplex
Because HSV-1 and HSV-2 are the types people most often need to test for, it’s worth understanding how testing works and where it falls short. The most reliable method is a swab taken directly from an active blister or sore that hasn’t yet crusted over. These tests, which detect the virus’s genetic material, work best when lesions are fresh.
Blood tests look for antibodies your body produces in response to infection rather than the virus itself. They can distinguish between HSV-1 and HSV-2 but come with a notable limitation: the chance of a false positive is much higher than with tests for STIs like chlamydia or gonorrhea. Current herpes blood tests simply aren’t as precise. Timing also matters. After exposure, it can take up to 16 weeks for antibodies to reach detectable levels, so testing too soon after a possible infection can produce a false negative.