Herpesviridae

The Herpesviridae is a family of DNA viruses that cause diseases in humans and animals. The family name is derived from the Greek herpein ("to creep"), referring to the latent, re-occurring infections typical of this group of viruses. Herpesviridae can cause latent or lytic infections.

Human herpesviridae

There are eight types of viruses in this family known to cause disease in humans. These viruses are (HHV stands for human herpesviruses):

HHV-1 = HSV-1 (herpes simplex virus 1): causes oral and/or genital herpes (predominantly orofacial)
HHV-2 = HSV-2 (herpes simplex virus 2): causes oral and/or genital herpes (predominantly genital)
HHV-3 = VZV (varicella zoster virus): causes chickenpox and shingles
HHV-4 = EBV (Epstein-Barr virus), lymphocryptovirus: causes infectious mononucleosis, Burkitt's lymphoma and nasopharyngeal carcinoma
HHV-5 = CMV (cytomegalovirus): causes infectious mononucleosis, retinitis, etc.
HHV-6 = Human B-cell lymphotrophic virus or roseolovirus: causes "sixth disease" (known as roseola infantum or exanthem subitum)
HHV-7 = closely related to HHV-6; causes roughly the same symptoms
HHV-8 = a type of rhadinovirus = KSHV = Kaposi's sarcoma-associated herpesvirus: causes Kaposi's sarcoma, primary effusion lymphoma and some types of multicentric Castleman's disease

Viral structure

The human herpesviruses all share some common properties. One shared property is virus structure - all herpesviruses are composed of relatively large double-stranded, linear DNA genomes encoding 100-200 genes encased within an icosahedral protein cage called the capsid which is itself wrapped in a lipid bilayer membrane called the envelope. This particle is known as the virion.

Following binding of viral envelope protein to cell membrane receptors, the virion is internalized and dismantled, allowing viral DNA to migrate to the cell nucleus. Within the nucleus, viral DNA undergoes limited replication and transcription of a small number of viral genes termed latency associated transcript (LAT). In this fashion the virus can persist in the cell (and thus the host) indefinitely. Reactivation of latent viruses has been implicated in a number of organic diseases. While primary infection is often accompanied by a self-limited period of clinical illness, long-term latency is symptom-free. Following activation, the virus switches on transcription of multiple additional non-latent genes termed lytic genes that lead to enhanced replication and virus production. Often, lytic activation leads to cell death. Clinically, lytic activation is often accompanied by emergence of non-specific symptoms such as low grade fever, headache, sore throat, malaise, rash, etc as well as clinical signs such as swollen or tender lymph nodes and immunological findings such as reduced levels of natural killer cells.

Animal herpesviridae

Subfamily Alphaherpesvirinae
- Genus Simplexvirus
  - Bovine herpesvirus 2 causes bovine mammillitis and pseudo-lumpyskin disease.
  - Cercopithecine herpesvirus 1, also known as Herpes B virus, causes a Herpes simplex-like disease in Macaques.
- Genus Varicellovirus
  - Bovine herpesvirus 1 causes infectious bovine rhinotracheitis, vaginitis, balanoposthitis, and abortion in cattle.
  - Bovine herpesvirus 5 causes encephalitis in cattle.
  - Caprine herpesvirus 1 causes conjunctivitis and respiratory disease in goats.
  - Porcine herpesvirus 1 causes pseudorabies.
  - Equine herpesvirus 1 causes abortion in horses.
  - Equine herpesvirus 3 causes coital exanthema in horses.
  - Equine herpesvirus 4 causes rhinopneumonitis in horses.
  - Canine herpesvirus 1 causes a severe hemorrhagic disease in puppies.
  - Feline herpesvirus 1 causes feline viral rhinotracheitis and keratitis in cats.
  - Duck herpesvirus 1 causes duck plague.
- Genus Mardivirus
  - Gallid herpesvirus 2 causes Marek's disease.
- Genus Iltovirus
  - Gallid herpesvirus 1 causes infectious laryngotracheitis in birds.
Subfamily Betaherpesvirinae
- Porcine herpesvirus 2 causes inclusion body rhinitis in swine.
Subfamily Gammaherpesvirinae
- Genus Rhadinovirus
  - Alcelaphine herpesvirus 1 causes bovine malignant catarrhal fever.
  - Bovine herpesvirus 4
  - Equine herpesvirus 2 causes equine cytomegalovirus infection.
  - Equine herpesvirus 5

Taxonomy

The following genera are included here:

Subfamily Alphaherpesvirinae
- Genus Simplexvirus; type species: Human herpesvirus 1 or Herpes simplex; diseases: cold sores, genital herpes
- Genus Varicellovirus; type species: Human herpesvirus 3 or Varicella-zoster virus; diseases: chickenpox, shingles
- Genus Mardivirus; type species: Gallid herpesvirus 2
- Genus Iltovirus; type species: Gallid herpesvirus 1
Subfamily Betaherpesvirinae
- Genus Cytomegalovirus; type species: Human herpesvirus 5
- Genus Muromegalovirus; type species: Murid herpesvirus 1
- Genus Roseolovirus; type species: Human herpesvirus 6; diseases: multiple sclerosis, chronic fatigue syndrome, cancer
Subfamily Gammaherpesvirinae
- Genus Lymphocryptovirus; type species: Human herpesvirus 4 or Epstein-Barr virus; diseases: mononucleosis, Burkitt's lymphoma, chronic fatigue syndrome
- Genus Rhadinovirus; type species: Human Herpesvirus 8, Saimiriine herpesvirus 2
Unassigned
- Genus Cercopithecine ; type species: Cercopithecine herpesvirus 1
- Genus Ictalurivirus; type species: Ictalurid herpesvirus 1

References

On Herpes I & II (for laymen or health care providers) The Truth About Herpes by the late Dr. Sacks.

External links

The most comprehensive information source on herpes is IHMF - a forum all virtually all peer reviewed medical literature on herpes. IHMF contains algorithms, flow charts, best management practices, epidemiology, state of the art research and so forth.