Latency of Herpes viruses

Herpes virus infects sensory neuron

the virus can miagrate in the sensory neuuron to the ganglia such as the gangilia of the trigeminal nerve.

The trigeminal nerve is one of the crainal nerves

The virus can stay in the ganglia for years and not be attacked by the immune system:

the virus is in the latent phase.

For some reason, the latent virus, can migrate from the ganglion to the sensory

end of the neuron.

It can replicate and be released into the environment

the released virus can infect epithelial cells and cause a cold sore to form

Latency can also occur with other Herpes viruses

Varicella zoster:chicken pox virus

This is a common childhood infection with a generalized vesicular rash.

Vesicles appear as successive "crops", so that lesions of different ages are present at the same time.

In children the disease is usually trivial and complications are rare.

If infection is delayed until adulthood the disease may be more severe and complications more frequent.

Infection is transmitted either by respiratory droplets or by direct contact with skin lesions.

Varicella is followed by long lasting immunity.

(http://www.uct.ac.za/depts/mmi/jmoodie/vzv2.html)

shingles is a result of a latent chicken pox viruses becoming active again

Therapy for herpes outbreak
ACYCLOVIR :Nucleoside anologue of Guanosine.
It is converted to acyclovir-tri-phosphate in herpesvirus-infected cells:

ACTIVE FORM During viral DNA replication, the viral DNA polymerase incorporates Acyclovir-TP into the growing DNA chain. This interferes with viral DNA synthesis by:
Binding irreversibly and blocking the viral DNA polymerase, and causes chain termination of the viral DNA
NB! Only HSV and VZV are sensitive to acyclovir.

(http://www.uct.ac.za/depts/mmi/jmoodie/vzv2.html)