There are eight known human herpesviruses, and they cause a surprisingly wide range of illnesses, from cold sores and chickenpox to mono and certain cancers. What ties them together is a shared behavior: once you’re infected, the virus stays in your body for life, hiding in cells and potentially reactivating later. Most people carry at least one type, often without knowing it.
HSV-1: Oral Herpes
Herpes simplex virus type 1 is the most common herpesvirus worldwide. It spreads through oral contact, mainly via saliva, sores, or skin around the mouth. Most people pick it up during childhood from a kiss or shared utensil. The classic sign is a cold sore on or around the lips, though many carriers never develop visible symptoms.
HSV-1 can also cause genital herpes when transmitted through oral sex. An estimated 376 million people had genital HSV-1 infections as of 2020, according to WHO data. Genital infections caused by HSV-1 tend to recur far less frequently than those caused by HSV-2, so many people with genital HSV-1 experience one outbreak and then rarely or never have another.
HSV-2: Genital Herpes
Herpes simplex virus type 2 spreads through sexual contact with genital or anal skin, sores, or fluids. It primarily causes genital herpes and is much more likely to cause recurring outbreaks than HSV-1 in the same location. Around 520 million people aged 15 to 49 were living with HSV-2 in 2020, and it’s possible to carry both types simultaneously. Roughly 50 million people do.
Combined, genital herpes from both virus types affects more than one in five adults globally. Many people with HSV-2 shed the virus even when they have no symptoms, which is a major reason it spreads so effectively. Antiviral medications can shorten outbreaks and reduce transmission risk, and daily suppressive therapy is an option for people who experience frequent recurrences.
Varicella-Zoster Virus (HHV-3)
This is the virus behind two distinct diseases: chickenpox on first infection and shingles when it reactivates years or decades later. During chickenpox, a characteristic itchy rash spreads across the body, progressing rapidly from flat red spots to raised bumps to fluid-filled blisters that eventually crust over. Lesions at different stages appear at the same time, which is one way doctors distinguish it from other rashes. Adults may also experience a day or two of fever and fatigue before the rash appears.
After recovery, the virus retreats into nerve cells near the spine and stays dormant. In some people, particularly those over 50 or with weakened immune systems, it reactivates as shingles: a painful, blistering rash that typically appears in a band on one side of the body. A vaccine is available for both chickenpox (given in childhood) and shingles (recommended for adults 50 and older). Recovery from chickenpox usually provides lifelong immunity to that illness, but it doesn’t prevent shingles from developing later.
Epstein-Barr Virus (HHV-4)
Epstein-Barr virus is best known as the cause of infectious mononucleosis, commonly called mono or “the kissing disease.” It spreads through saliva and is extremely common. Most people contract it at some point in their lives, often during adolescence or young adulthood. Symptoms of mono include severe fatigue, sore throat, swollen lymph nodes, and fever that can last weeks.
EBV is also linked to certain cancers, including some lymphomas and nasopharyngeal carcinoma. Like all herpesviruses, it remains in the body permanently after the initial infection. Most carriers never experience problems beyond the initial illness, but in people with compromised immune systems, the virus can reactivate and cause complications.
Cytomegalovirus (HHV-5)
Cytomegalovirus infects a large portion of the population and rarely causes noticeable symptoms in healthy adults. When it does, the illness can look similar to mono: fatigue, mild fever, and body aches. The real danger is for two groups: people with weakened immune systems and developing fetuses.
In transplant recipients or people living with HIV, CMV can reactivate and damage organs. For pregnant women, a new CMV infection can be passed to the fetus, causing congenital CMV. This is a leading infectious cause of hearing loss in newborns and can result in vision problems, developmental delays, and pregnancy loss. There is no widely available CMV vaccine yet, which makes awareness especially important for people who are pregnant or planning to become pregnant.
HHV-6 and HHV-7: Roseola
These two closely related viruses primarily affect infants and toddlers between 6 months and 3 years old. HHV-6 is the main cause of roseola, a common childhood illness with a distinctive pattern: a high fever (often 103 to 105°F) appears suddenly and lasts 3 to 5 days with no other obvious symptoms. Just as the fever breaks, 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 is sometimes so mild it goes unnoticed.
The timing is what makes roseola recognizable. The rash arrives precisely when the fever disappears, which can actually be reassuring to parents since it signals the illness is ending. Most children recover without complications, and HHV-7 causes a similar but generally milder illness. Nearly all children have been infected with HHV-6 by the time they reach school age.
HHV-8: Kaposi Sarcoma-Associated Herpesvirus
HHV-8 is the least common of the human herpesviruses and the most closely tied to cancer. It causes Kaposi sarcoma, a type of cancer that produces dark-colored skin lesions and can also affect the mouth, lungs, and digestive tract. There are four recognized forms of the disease based on who it affects:
- Epidemic (AIDS-related) KS occurs most often in people with advanced HIV/AIDS and was one of the first conditions that helped identify the AIDS epidemic.
- Classic KS mainly affects older men of Eastern European, Middle Eastern, and Mediterranean descent.
- Transplant-associated KS develops in organ transplant recipients taking immune-suppressing medications.
- Endemic (African) KS affects people of all ages in parts of Africa, including a childhood form that can spread through lymph nodes and internal organs.
The common thread across all four types is a weakened or altered immune response. In people with healthy immune systems, HHV-8 infection rarely causes disease.
Rare but Serious Complications
Most herpesvirus infections are manageable or go unnoticed entirely, but severe complications can occur. The most dangerous is herpes simplex encephalitis, a brain infection caused primarily by HSV-1. It affects roughly 2 to 4 people per million each year worldwide and causes rapid-onset fever, headache, seizures, confusion, and neurological damage. It’s the most common cause of fatal sporadic encephalitis in the United States. Early treatment with antiviral medication is critical and dramatically improves survival.
Neonatal herpes is another serious concern. HSV can be transmitted from mother to baby during delivery, particularly if the mother has an active genital outbreak. This can cause widespread infection in the newborn and is one reason why pregnant women with a history of genital herpes are often offered antiviral therapy starting at 36 weeks of pregnancy.
How Herpesviruses Are Diagnosed
When symptoms are present, the most reliable test for HSV is a PCR swab taken directly from a sore or blister. PCR testing is highly sensitive and specific, meaning it catches infections that other methods miss and rarely gives false results. Viral culture (growing the virus from a sample in a lab) is also highly specific but less sensitive than PCR, especially for samples taken from sites other than active lesions.
Blood tests that detect antibodies can determine whether you’ve been exposed to HSV-1 or HSV-2 in the past, but they can’t tell you when or where you were infected. Antibody testing is less useful for diagnosing a current outbreak and is generally reserved for situations where a swab isn’t possible. For varicella, EBV, and CMV, blood tests are the standard diagnostic approach since these infections are usually identified by the immune response rather than by swabbing a lesion.