Human herpesviruses (HHV) are a group of eight different viruses known to cause a wide range of diseases in humans. These viruses are part of the herpesviridae family, 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 specific infections, ranging from mild symptoms such as herpes to more serious diseases such as shingles, mononucleosis, and even certain types of cancer. . This comprehensive overview details the characteristics, classification, clinical manifestations, diagnostic methods, and treatments associated with eight human herpesviruses (HHV 1-8). Understanding these viruses is essential to recognize viral symptoms, manage viral reactivation, and prevent complications, especially in those at high risk for severe outcomes from these infections. Important in immunocompromised people.
What is a herpes virus?
Herpesviruses are spherical, large (150-200 nm in diameter), enveloped, double-stranded DNA viruses. They replicate within the nucleus of the host cell, establish a latent infection, and persist indefinitely within the infected host. Reactivation occurs frequently, especially in immunocompromised people.
Human herpesvirus (HHV)
There are more than 100 known herpesviruses, and most of them infect animals such as cows, goats, dogs, cats, horses, pigs, rodents, birds, reptiles, and fish. There are eight types of herpesviruses that cause disease in humans, known as human herpesviruses (HHVs). In addition, two other herpesviruses that can infect humans include:
- Monkey B virus (herpesvirus simiae)
- Murad herpesvirus 68 (MHV-68)
Classification of herpesviruses: understanding subfamilies and genera
Herpesviruses are classified as follows: herpes virus order, herpesviridae family, and Alphaherpesviridae subfamily. These are further divided into genera based on specific characteristics and biological properties.
Herpesvirus subfamilies:
- alphaherpesvirus
- Genus: simplex virus (HHV-1, HHV-2), chickenpox virus (HHV-3)
- betaherpesvirus
- Genus: cytomegalovirus (HHV-5), roseolovirus (HHV-6, HHV-7)
- gammaherpesvirus
- Genus: Lymph Cryptovirus (HHV-4), Radinovirus (HHV-8)
Biological characteristics of herpesviruses:
- alphaherpesvirus (e.g., HSV-1, HSV-2, VZV) have short growth cycles (approximately 18 hours) and tend to be cytolytic. Their latent infection resides primarily in neurons.
- betaherpesvirus (CMV, HHV-6, etc.) have a long replication cycle (approximately 70 hours) and can infect the glands and kidneys.
- gammaherpesvirus (e.g., EBV, HHV-8) cause lymphoproliferative diseases and primarily infect lymphoid tissues.
herpes simplex virus (HSV)
HSV consists of two types. HSV-1 and HSV-2differentiated based on. DNA structure, antigenic, tissue orientationand Growth patterns in cell culture. HSV-1 is usually transmitted through oral contact, while HSV-2 is more commonly transmitted through sexual intercourse.
Clinical symptoms and infections:
Both HSV-1 and HSV-2 can cause similar clinical symptoms. However, HSV-1 usually affects the upper body, especially the oropharyngeal area, whereas HSV-2 mainly affects the genital area. There is no significant mutual protection between the two types.
- oropharyngeal infection: Often asymptomatic or causes acute gingivostomatitis. Recurrent outbreaks usually occur at the lip margins.
- skin infection: Health care workers (HCWs) who come into contact with oral secretions may become ill. herpetic hail (finger infection). Athletes (such as wrestlers) are also at risk of: herpes xiph.
- herpetic eczema: A severe skin infection in people with eczema that can be fatal if untreated.
- eye infection: Herpetic keratoconjunctivitisIt is usually caused by HSV-1 and can cause corneal scarring and vision loss if left untreated.
- central nervous system infection: Can be caused by HSV herpes meningitis or HSV encephalitisthe latter is a life-threatening condition.
Neonatal HSV infection
Neonatal herpes can be congenital (transplacental) or obtained at birth. The risk of infection is higher if the mother is in the process of seroconversion near birth.
Newborn symptoms:
- disseminated disease (The liver and other organs are affected, often with skin lesions).
- encephalitis: Can occur with or without skin lesions.
- Involvement of the skin, eyes, and mouth: Often seen after 10 days of birth.
diagnosis Neonatal HSV includes:
- Isolation of HSV from skin, CSF, or other body fluids
- NAAT for detection in CSF
- Exclusion of other infections such as CMV, VZV, rubella, and enteroviruses
Diagnosis of HSV infection
Various diagnostic methods are used to detect HSV.
- serology: IgG and IgM antibody tests, but are not reliable in determining timing of infection or viral activity.
- microscopy: Tzanck smear, but mainly replaced by PCR, DFA, and culture methods.
- culture: HSV proliferates rapidly in cell culture, and HSV-1 and HSV-2 can be distinguished by typing.
- molecular methods: NAAT is more sensitive than culture and is the preferred diagnostic method for differentiating HSV types.
Varicella-zoster virus (VZV)
Causes of VZV Chickenpox (varicella) with the kids Shingles (herpes zoster) For adults.
Chickenpox (varicella)
- contagion; infection: Highly contagious, primarily through direct contact with respiratory droplets or fluid from vesicles.
- symptoms: Characterized by a centripetal rash, usually starting on the trunk and progressing to the extremities. Lesions occur on successive crops.
Shingles (herpes zoster)
- reactivation The presence of latent VZV in the dorsal root ganglion usually results in focal vesicular lesions along the dermatome.
- pain It is often severe in affected areas.
Diagnosis and vaccination
- diagnosis: Based on clinical symptoms, serology, Tzanck smear, DFA, and PCR.
- vaccination: Can be used for both chickenpox and shingles. Passive immunization with varicella/shingles immune globulin can also be used in people with weakened immune systems.
Human herpesvirus 6 (HHV-6) and 7 (HHV-7)
HHV-6 is divided into two subspecies. HHV-6A and HHV-6Band HHV-6B is the main cause of Sudden rash (sixth disease)also known as infant roseola.
Symptoms of the sixth disease:
- A sudden onset of high fever is followed by a rash that usually starts on the trunk and spreads to the extremities.
HHV-7, discovered in 1990, also causes: roseola There are similarities with HHV-6. Both viruses belong to: roseolovirus Genus.
Epstein-Barr virus (EBV) – HHV-4
EBV is one of the most common human viruses; 90% of people around the world I’ll get infected someday. It is primarily transmitted through oropharyngeal secretions and is known to cause infections. Infectious mononucleosis (IM).
Clinical symptoms:
- infectious mononucleosis: Also known as the “kissing disease,” this disease is characterized by fever, sore throat, and swollen lymph nodes.
- EBV is also associated with various cancers. Burkitt lymphoma, hodgkin lymphomaand Nasopharyngeal cancer.
diagnosis:
- serology: Detection of antibodies against EBV antigens (VCA, EA, EBNA).
- molecular methods: NAAT for detecting EBV DNA.
- histology: In situ hybridization can be used to visualize EBV infection within tissues.
Cytomegalovirus (CMV) – HHV-5
CMV is a common virus that can cause serious complications in immunocompromised people and newborns. Mainly sent via body fluid saliva, blood, breast milk, etc.
Symptoms in healthy people:
- It has mild flu-like symptoms, but is often asymptomatic.
Congenital CMV:
- may cause hearing loss, visual impairmentneonatal developmental delay.
- CMV is the most common infectious cause of birth defects in the United States
Diagnosis of CMV:
- virus culture: Suitable for detecting CMV in newborns.
- NAAT: PCR to detect CMV DNA.
- Antigen detection: ELISA and IFA for detection of CMV antigen in body fluids.
- serology: IgG and IgM tests for past and current infections.
Kaposi’s sarcoma-associated herpesvirus (HHV-8)
Associated with HHV-8 are: kaposi sarcomais a commonly occurring type of cancer. immunocompromised personespecially HIV/AIDS patients.
Real-time PCR (RT-PCR): Principles, Procedures, and Applications
