Virology

HERPESVIRIDAE FAMILY

Written by MicroDok

Herpesviridae family is a distinct viral family that contains a wide variety of viruses that are distributed worldwide and which infect humans, mammals and other vertebrates. There are three subfamilies that make up the Herpesviridae family, and they include Alphaherpesvirinae, Betaherpesvirinae, and Gammaherpesvirinae. Simplexvirus (e.g. herpes simplex virus) and Varicellovirus (e.g. Varicella-zoster virus) are the two genera of Alphaherpesvirinae that contain viruses that infect humans. In the Betaherpesvirinae subfamily, there are only two genera of viruses that infect humans; and these include Cytomegalovirus (that contain cytomegalovirus) and Roseolovirus (that contain human herpes virus types 6 and 7). Gammaherpesvirinae family has two genera viz: Lymphocryptovirus (that contain Epstein-Barr virus) and Rhadinovirus (that contain human herpesvirus 8).

Viruses in this family include herpes simplex virus (HSV) type 1 and 2 and Varicella zoster virus (VZV) in the Alphaherpesvirinae subfamily; cytomegalovirus (CMV) in the Betaherpesvirinae family; and Epstein-Barr virus (EBV) which is in the Gammaherpesvirinae subfamily. Morphologically, the herpes viruses have a dsDNA genome, and they measure about 150 nm or 100-300 nm in diameter. Structurally, herpes viruses have an icosahedral shape. They are enveloped viruses. Herpes viruses replicate in the nucleus and they are released from their host cell via budding through the cytoplasmic membrane of the infected cell. Chickenpox (caused by VZV), Burkitt’s lymphoma (a tumour caused by EBV), fever blisters or cold sores (caused by HSV-1) and genital herpes (caused by HSV-2) which are both caused by the human herpes simplex viruses type 1 and 2 respectively are typical examples of clinical diseases caused by viruses in the Herpesviridae family.

Some viruses in the Herpesviridae family such as CMV are common amongst individuals with weakened immune system especially AIDS patients Lesions or blisters on the penis (in males), vagina or cervix (in females) and blisters appearing on the lips and mouth regions of infected individuals are some of the clinical symptoms of the disease. Some of the route of transmission of the disease includes direct sexual contact with an infected individual, transmission via aerosols, and other body fluids such as saliva. Herpes simplex virus can also be transmitted from an infected mother to the unborn child. It is noteworthy that herpes viruses have the ability to establish a latent infection in their natural host; and thus the virus is capable of re-emerging in its virulence in the future in an asymptomatic host. Prophylaxis and antiviral therapy exist for the treatment of some human herpes virus infections.

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