The herpes family of viruses enter a latent (silent) phase of infection following initial infection, but can be reactivated resulting in recurrent infection.

Members of the herpes family of viruses are responsible for a number of different types of infection in humans and animals. Once humans become infected, they remain infected for life and may be infectious to others even when symptoms are not present. The cycle of infection involves exposure to the herpes virus followed by initial infection, latent infection and reactivation.

Initial Infection and Herpes Virus Replication

Herpes infection begins when the virus comes in contact with mucous membranes or broken skin. Glycoproteins in the outer virus coat (envelope) binds to the surface of epithelial cells and enters the cell by fusion of the virus envelope with the plasma membrane of the cell.

The virus replicates in epithelial cells (skin cells) and/or white blood cells (T-lymphocytes, B-lymphocytes and macrophages). Once inside the cell, the nucleocapsid (virus protein coat and genetic material) is transported to the host cell nucleus where viral DNA replication and nucleocapsid assembly occurs. The nucleocapsid is then released form the cell through the nuclear membrane.

Inflammation occurs and infected cells are destroyed.

During initial infection, herpes can spread through the lymphatic system to lymph nodes. The body’s immune system limits viral replication, prevents herpes infection from spreading further, and allows sores to heal.

Latent Infection

Within two days of initial infection, the herpes virus enters local sensory nerve cells and establishes a silent (latent) infection. During latency the viral genome remains stable in the nucleus of nerve cells or other latently infected cells.

Herpes Virus Reactivation and Recurrent Infection

Herpes viruses may become reactivated and travel from the nerve center (neuron) down the nerve cell to epithelial cells at the initial site of infection. A number of conditions or stimuli can reactivate the virus resulting in recurrent infection.

The severity of symptoms during recurrent infection vary greatly, influenced by the strength and numbers of replicating virus on one side and the ability of the immune system to prevent viral infection from spreading.

A number of factors can affect reactivation:

• Ultraviolet light (including sunshine)
• Suppression of the immune system
• Fever
• Trauma to latently infected nerve cells
• Pneumococcal pneumonia
• Stress

Symptoms may not always be present during recurrent infection: more severe initial infection is associated with more frequent and severe recurrent infection. People with recurrent infection can shed virus and be infectious to others regardless of whether or not they have symptoms.

Read more about herpes cirus infections:

Infections Caused by Herpes Virus

Animation of HSV Infection and Replication

Source:

Pertel PE and PG Spear. Biology of herpesviruses in Sexually Transmitted Diseases, Third Edition. McGraw-Hill, New York, 1999.