HERPESVIRIDAE FAMILY

Gammaherpesvirinae family has two genera viz: Lymphocryptovirus (that contain Epstein-Barr virus) and Rhadinovirus (that contain human herpesvirus 8). Viruses in the Herpesviridae 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.

Understanding the Herpesviridae Family

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 (Table 1).

Some viruses in the Herpesviridae family such as CMV are common amongst individuals with weakened immune systems, 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.     

    Table 1. Human herpes virus infections

SUBFAMILY	GENERA	VIRUS	TRANSMISSION ROUTE	DISEASE
Alphaherpesvirinae	Simplexvirus	Herpes simplex virus (HSV) 1   HSV-2	Body fluids such as saliva and blood   Body fluids from the penis, vagina or cervix	Fever blisters or cold sores on the lips   Genital ulcers
	Varicellovirus	Varicella zoster virus (VZV)	Aerosols from infected persons	Shingles and chickenpox
Betaherpesvirinae	Cytomegalovirus	Cytomegalovirus (CMV)	Body fluids such as saliva, blood and fluids from genital region	Pneumonia, retinitis and gastrointestinal disorder in immunocompromised individuals
	Roseolovirus	Human herpesvirus type 6	Body fluids such as saliva and blood	Sixth disease and multiple sclerosis in some cases
		Human herpesvirus type 7	Body fluids such as saliva and fluids from the genital region	Herpes latent infection (but there is still no clear involvement of herpesvirus type 7 in causing human disease)
Gammaherpesvirinae	Lymphocryptovirus	Epstein-Barr virus (EBV)	Body fluids such as saliva and blood	Burkitt’s lymphoma, infectious mononucleosis and Hodgkin’s lymphoma
	Rhadinovirus	Human herpesvirus type 8	Contact with body fluids (e.g. blood) of infected individuals	Kaposi’s sarcoma in immunocompromised patients such as people living with HIV/AIDS

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