Herpes viruses cause numerous diseases in humans. Classified as DNA viruses according to the type of genetic material they possess, herpes viruses are typically transmitted by close intimate contact, usually involving contact with infected body fluids or secretions. Infections are usually characterized by flareups interspersed by periods of latency (quiet periods without apparent disease). There are about 25 types of herpes viruses or more, with eight well known types involved in human infections.
Herpes Simplex Virus Type1 (Human Herpes Virus 1)
Herpes Simplex virus type 1 is typically spread by kissing and physical contact. The virus lodges in the nervous system, where it causes intermittent flare ups of disease. It attacks the skin around the upper parts of the body, the eyes, the mouth (cold sores) and the brain.
Herpes Simplex Virus Type2 (Human Herpes Virus2)
Herpes Simplex Virus Type2 is typically a sexually transmitted disease. It is also lodged in the nervous system. The virus typically causes genital herpes, attacking the skin around the genitals and the anus. It also attacks the covering of the brain and spinal cord, causing meningitis. This type is responsible for infections in newborns, which is often fatal.
Varicella Zoster virus (Human Herpes Virus 3)
This closely resembles the herpes simplex virus. It is transmitted through the respiratory route and physical contact. The virus also lodges in the nervous system. It causes chicken pox and shingles (intermittent flare-ups) in susceptible individuals. The virus also attacks babies in the womb, leading to birth defects. Infection in the newborn is often fatal.
Epstein-Barr Virus (Human Herpes Virus4)
This virus is transmitted through the saliva. It is lodged primarily in a particular blood cell called the B-Lymphocytes. This virus is capable of stimulating cells to develop forms that can lead to cancer. It causes infectious mononucleosis and Oral Hairy Leukoplakia (with HIV) in the United States. It is responsible for Burkitt's lymphoma in Africa and Naso-Pharyngeal cancer in Asia.
Cytomegalovirus (Human Herpes virus5)
This virus is spread by body secretions namely saliva, urine, semen, vaginal secretions and blood products. It usually causes low grade infections except in the unborn children, newborns and those with suppressed immunity. It causes congenital birth defects in babies and commonly fatal infections in the newborn. This virus is responsible for complicated infections in people with HIV. infections where it attacks the eyes (retinitis), lungs (pneumonia), intestines (colitis) and brain (encephalitis).
Other Herpes Viruses
Human Herpes Virus 6 and Human herpes virus7 are both implicated in Roseola Infantum in children, a typically self resolving infection with fever, rash and swollen lymph nodes. They also cause severe infections in those with compromised immunity. Human herpes virus8 is seen in the saliva of patients with H.I.V. that develop Kaposi 's sarcoma. It typically attacks the Lymphocytes in the blood.
Herpes B is seen in monkeys from where it can be transmitted to humans. It causes nervous system disease in human beings that are infected.
