Human herpesviruses (HHV) are a group of eight different viruses known to cause a variety of diseases in humans. These viruses belong to the family Herpesviridae, which also includes other viruses that affect animals. Human herpesviruses are divided into three subfamilies based on their genetic and biological characteristics: alpha, beta, and gamma herpesviruses. Each type of herpes virus causes a specific infection, ranging from minor conditions like cold sores to more serious illnesses like shingles, mononucleosis, and even some types of cancer. This comprehensive overview will provide an in-depth exploration of the characteristics, classification, clinical manifestations, diagnostic approaches, and treatment associated with the eight human herpesviruses (HHV 1-8). Understanding these viruses is critical to recognizing their symptoms, managing their reactivation, and preventing complications, especially in immunocompromised individuals who are at higher risk for serious consequences from these infections.
What is herpes virus?
Herpesviruses are spherical, large (150-200 nm in diameter), enveloped, double-stranded DNA viruses. They replicate in the nucleus of the host cell, establish a latent infection, and persist indefinitely in the infected host. Reactivation is common, especially in immunocompromised individuals.
Human Herpes Virus (HHV)
Although there are more than 100 known herpes viruses, most infect animals, including cattle, goats, dogs, cats, horses, pigs, rodents, birds, reptiles and fish. There are eight types of herpes viruses that cause disease in humans, called human herpes viruses (HHV). Additionally, two other herpes viruses that infect humans include:
- Simian B virus (simian herpesvirus)
- Murine herpesvirus 68 (MHV-68)
Herpesvirus Classification: Understanding Subfamilies and Genus
Herpes viruses are classified as Herpesvirales Order, Herpesviridae family, and Herpesvirinae A Subfamily. They are further divided into genera based on specific characteristics and biological properties.
Herpesvirinae:
- alphaherpes virus
- Genus: Simplevirus (HHV-1, HHV-2), Varicella virus (HHV-3)
- betaherpesvirus
- Genus: cytomegalovirus (HHV-5), Rosevirus (HHV-6, HHV-7)
- gammaherpesvirus
- Genus: lymphocytovirus (HHV-4), Rhinovirus (HHV-8)
Biological properties of herpes viruses:
- alphaherpes virus (e.g., HSV-1, HSV-2, VZV) tend to have short growth cycles (approximately 18 hours) and are cytolytic. Their latent infection is primarily located in neurons.
- betaherpesvirus (e.g., CMV, HHV-6) have a long growth cycle (approximately 70 hours) and infect glands and kidneys.
- gammaherpesvirus (e.g., EBV, HHV-8) cause lymphoproliferative diseases and primarily infect lymphoid tissue.
Herpes simplex virus (HSV)
HSV includes two types: herpes simplex virus 1 and herpes simplex virus 2differentiate according to its DNA structure, Antigenic properties, organizational orientationand Growth patterns in cell culture. HSV-1 is usually spread through oral contact, while HSV-2 is more commonly spread through sexual intercourse.
Clinical manifestations and infection:
Both HSV-1 and HSV-2 can cause similar clinical symptoms. However, HSV-1 typically affects the upper body, especially the oropharyngeal area, while HSV-2 primarily affects the genital area. There was no significant cross-protection between the two types.
- oropharyngeal infection: Usually asymptomatic or causing acute gingivostomatitis. Recurrent eruptions usually occur on the lip edges.
- skin infection: Healthcare workers (HCW) exposed to oral secretions may suffer from Banded scrofula (finger infection). Athletes (such as wrestlers) are also at risk for: gladiator herpes.
- herpetic eczema: A serious skin infection in people with eczema that can be fatal if left untreated.
- eye infection: herpetic keratoconjunctivitisOften caused by HSV-1, if left untreated, it can cause corneal scarring and vision loss.
- central nervous system infection: HSV may cause herpetic meningitis or herpes simplex virus encephalitisthe latter is a life-threatening condition.
Neonatal HSV infection
Neonatal herpes may be congenital (transplacental) or obtained during childbirth. The risk of infection is higher if the mother is in the process of seroconversion close to delivery.
Newborn symptoms:
- infectious disease (Involving organs such as the liver, often accompanied by skin lesions).
- encephalitis: May be associated with or without skin damage.
- Skin, eye, mouth involvement: More common after 10 days of age.
diagnosis Neonatal HSV includes:
- Isolation of HSV from skin, cerebrospinal fluid, or other body fluids
- NAAT for cerebrospinal fluid testing
- Rule out other infections such as CMV, VZV, rubella, and enterovirus
Diagnosis of HSV infection
HSV can be detected using a variety of diagnostic methods:
- Serology: IgG and IgM antibody tests, but are not reliable for determining time of infection or viral activity.
- microscopy: Tzanck smear test, although largely superseded by PCR, DFA, and culture methods.
- culture: HSV grows rapidly in cell culture, and typing can differentiate between HSV-1 and HSV-2.
- molecular methods: NAAT is more sensitive than culture and is the diagnostic method of choice for differentiating HSV types.
Varicella zoster virus (VZV)
Varicella zoster virus causes Chickenpox (chickenpox) in children and Shingles (herpes zoster) in adults.
Chickenpox (chickenpox)
- infect: Highly contagious, mainly through respiratory droplets or direct contact with vesicle fluid.
- symptom: Characterized by a central rash that usually starts on the trunk and progresses to the extremities. Lesions appear in successive crops.
Shingles (herpes zoster)
- Re-enable Latent VZV in the dorsal root ganglia causes localized vesicular lesions, usually along the dermatomes.
- pain The situation in affected areas is often severe.
Diagnosis and vaccination
- diagnosis: Based on clinical presentation, serology, Tzanck smear, DFA and PCR.
- Vaccination: Suitable for chickenpox and shingles. Immunocompromised individuals can also be passively immunized with varicella zoster immune globulin.
Human herpesvirus types 6 (HHV-6) and 7 (HHV-7)
HHV-6 is divided into two variants: HHV-6A and HHV-6Band HHV-6B is the main reason for Rash (sixth disease)also known as infantile roseola.
Symptoms of the sixth disease:
- A sudden high fever, followed by a rash that usually starts on the trunk and spreads to the extremities.
HHV-7, discovered in 1990, is responsible for Roseola There are similarities with HHV-6. Both viruses belong to Rosevirus genus.
Epstein virus (EBV) – HHV-4
EBV is one of the most common human viruses, 90% of people in the world Be infected at some point. It is transmitted primarily through oropharyngeal secretions and is known to cause Infectious mononucleosis (IM).
Clinical manifestations:
- infectious mononucleosis: Commonly known as the “kissing disease,” it is characterized by fever, sore throat, and swollen lymph nodes.
- EBV has also been linked to a variety of cancers, including Burkitt lymphoma, Hodgkin lymphomaand Nasopharyngeal cancer.
diagnosis:
- Serology: Detects antibodies against EBV antigens (VCA, EA, EBNA).
- molecular methods:NAAT detects EBV DNA.
- Histology: In situ hybridization can be used to observe EBV infection in tissues.
Cytomegalovirus (CMV) – HHV-5
CMV is a common virus that can cause serious complications in immunocompromised individuals and neonates. It mainly passes body fluid Such as saliva, blood and breast milk.
Symptoms in healthy people:
- Mild flu-like symptoms, usually asymptomatic.
Congenital cytomegalovirus:
- will lead to hearing loss, visual impairmentand neonatal developmental delays.
- CMV is the most common infectious cause of birth defects in the United States
Diagnosis of Cytomegalovirus:
- viral culture: Preferred for detecting neonatal CMV.
- NAAT: PCR for detection of CMV DNA.
- Antigen test: ELISA and IFA are used to detect CMV antigen in body fluids.
- Serology: IgG and IgM testing for past and active infections.
Kaposi’s sarcoma-associated herpesvirus (HHV-8)
HHV-8 and Kaposi’s sarcomaa common type in Immunocompromised individualsespecially those living with HIV/AIDS.
Real-time PCR (RT-PCR): Principles, Procedures and Applications
