Herpesviruses are a widespread family of viruses that commonly infect humans, establishing a lifelong presence within the body. Many individuals unknowingly carry these viruses. A defining characteristic is their ability to become dormant after initial infection, reactivating later to cause recurring symptoms.
Defining Herpesviruses
Herpesviruses are large, enveloped viruses containing a double-stranded DNA genome. This genetic material is housed within a protein shell (capsid), surrounded by a layer of proteins (tegument), and encased in a lipid envelope. Upon entering a host cell, the viral DNA circularizes and is maintained in the nucleus as multiple copies.
A key feature is their capacity for latency, where the virus remains inactive within specific host cells without actively replicating. During this dormant phase, viral gene expression is limited, helping the virus evade the immune system. The viral genome persists within the host, ready to reactivate under certain conditions.
Major Herpesvirus Types and Associated Conditions
Herpes Simplex Virus Type 1 (HSV-1)
Herpes Simplex Virus Type 1 (HSV-1) is highly prevalent. It typically manifests as cold sores or fever blisters around the mouth or on the face. While primarily associated with oral infections, HSV-1 can also cause genital herpes through oral-genital contact. HSV-1 infection can lead to severe complications like encephalitis (brain inflammation) or keratitis (eye infection). Recurrent outbreaks are common.
Herpes Simplex Virus Type 2 (HSV-2)
Herpes Simplex Virus Type 2 (HSV-2) is the primary cause of genital herpes. This infection typically presents as blisters or sores on or around the genitals, anus, buttocks, or inner thighs. Sores can also develop internally, such as within the vagina. While often causing noticeable outbreaks, many people with HSV-2 infection remain asymptomatic. Similar to HSV-1, severe complications like meningitis or encephalitis can occur.
Varicella-Zoster Virus (VZV)
Varicella-Zoster Virus (VZV), also known as human herpesvirus 3 (HHV-3), is responsible for two distinct conditions: chickenpox and shingles. Chickenpox (varicella) is the initial infection, characterized by an itchy, blister-like rash that typically starts on the chest, back, and face before spreading. After the primary chickenpox infection resolves, VZV resides in sensory nerves. Years or decades later, the virus can reactivate, causing shingles (herpes zoster). Shingles presents as a painful, blistering rash that follows a specific nerve pathway, commonly affecting the face or trunk.
Epstein-Barr Virus (EBV)
Epstein-Barr Virus (EBV), or human herpesvirus 4 (HHV-4), is a common human virus. It is the primary cause of infectious mononucleosis, often called “mono” or “glandular fever.” This illness commonly affects teenagers and young adults, leading to symptoms like extreme fatigue, fever, sore throat, and swollen lymph nodes. While most infections are mild or asymptomatic, fatigue can persist for months in some individuals. The virus can also cause spleen or liver enlargement.
Cytomegalovirus (CMV)
Cytomegalovirus (CMV), or human herpesvirus 5, is a very common herpesvirus. Most healthy individuals infected with CMV experience no symptoms or a mild illness resembling mononucleosis, characterized by fever, fatigue, and swollen glands. Unlike EBV, CMV mononucleosis typically does not cause a severe sore throat. CMV poses a greater concern for infants infected before birth (congenital CMV) and individuals with weakened immune systems. Congenital CMV can lead to serious health issues in newborns, including hearing loss, developmental delays, and vision problems. In immunocompromised individuals, CMV reactivation can cause severe disease, affecting organs like the eyes (CMV retinitis), lungs (pneumonia), or brain (encephalitis).
Human Herpesvirus 6 and 7 (HHV-6, HHV-7)
Human Herpesvirus 6 (HHV-6) and Human Herpesvirus 7 (HHV-7) are most commonly associated with roseola, also known as exanthem subitum or sixth disease. This childhood illness typically affects infants and very young children. The infection often begins with a sudden high fever, sometimes reaching 103°F (39.4°C), which lasts for three to five days. As the fever subsides, a characteristic rose-pink or red rash appears, usually starting on the chest and back before spreading to the neck and arms. This rash is generally not itchy or painful and fades within a few hours to a couple of days. While roseola is usually a mild and self-limiting illness, high fevers can occasionally trigger febrile seizures in children.
Kaposi’s Sarcoma-Associated Herpesvirus (KSHV/HHV-8)
Kaposi’s Sarcoma-Associated Herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8), is linked to certain cancers and lymphoproliferative disorders. It is the causative agent of Kaposi’s sarcoma, a cancer that develops from the cells lining blood and lymphatic vessels. This cancer often appears as bluish-red or purple bumps or patches on the skin, but can also affect mucous membranes and internal organs. Most infected individuals with healthy immune systems will not develop Kaposi’s sarcoma. The disease primarily occurs in people with weakened immune systems, including those with HIV/AIDS or organ transplant recipients. KSHV has also been associated with other conditions, including primary effusion lymphoma and multicentric Castleman’s disease.
Transmission and Viral Latency
Herpesviruses spread through various modes. Herpes simplex viruses (HSV-1 and HSV-2) transmit through direct person-to-person contact, often involving skin-to-skin contact with active sores, saliva, or other bodily secretions, including kissing or sexual contact. Varicella-Zoster Virus (VZV) is highly contagious and spreads through airborne respiratory droplets or direct contact with fluid from lesions. Epstein-Barr Virus (EBV) and Human Herpesvirus 6 and 7 (HHV-6/7) are commonly transmitted through saliva. Cytomegalovirus (CMV) can spread through various body fluids, including saliva, urine, semen, and breast milk, and can also transmit from a pregnant person to their baby. Kaposi’s Sarcoma-Associated Herpesvirus (KSHV) transmission is less understood but is thought to occur through sexual contact, saliva, or from mother to child.
Following initial infection, herpesviruses establish latency, where the viral genome persists within specific host cells without active replication. For alphaherpesviruses like HSV-1, HSV-2, and VZV, the virus resides in the nuclei of nerve cells. Gammaherpesviruses such as EBV and KSHV establish latency in B cells, while betaherpesviruses like CMV and HHV-6/7 can maintain latency in various cell types, including leukocytes and salivary glands. Reactivation, which can lead to recurrent symptoms and viral shedding, can be triggered by factors such as physical or emotional stress, other illnesses, immunosuppression, hormonal changes, or sunlight exposure.
Detection and Management
Diagnosing herpesvirus infections often involves a combination of clinical examination and laboratory tests. A healthcare provider may visually inspect any lesions or rashes. For confirmation, laboratory tests can be performed, such as viral culture, where a sample from a sore is grown in a lab to identify the virus. Polymerase chain reaction (PCR) tests are highly sensitive and can detect viral DNA in various samples, providing a definitive diagnosis. Blood tests can also detect antibodies against specific herpesviruses, indicating a past infection, even if no current symptoms are present.
Management of herpesvirus infections primarily focuses on reducing symptoms, decreasing the frequency and severity of outbreaks, and minimizing transmission. Antiviral medications are the mainstay of treatment. Commonly prescribed antivirals include acyclovir, valacyclovir, and famciclovir. These medications work by interfering with the virus’s ability to replicate its DNA, effectively slowing or stopping viral reproduction. They can be used as episodic therapy to treat individual outbreaks, shortening their duration and severity, or as daily suppressive therapy to prevent recurrences. Symptomatic relief for pain and discomfort can be achieved with over-the-counter pain relievers like paracetamol or ibuprofen, and topical numbing creams. Preventive measures include avoiding direct contact during active outbreaks, practicing safe sex with consistent condom use, and for VZV, vaccination is available to prevent chickenpox and reduce the risk of shingles.