Herpes zoster

Also known as shingles. 

Pathophysiology

This disease is caused by human alphaherpesvirus 3 (HHV-3) also known as varicella zoster virus (VZV). 

The initial infection by HHV-3 is called varicella. HHV-3 can enter spinal nerve roots and enter a dormant inactive state which allows it to hide from the immune system. 

Decades later, the HHV-3 can spontaneously reactivate, spread along the spinal nerves and infect the attached structures. This usually leads to an infection of the skin supplied by the infected spinal nervous (the dermatome). The symptoms are similar to varicella, but limited to the affected dermatomes. Often the infected nerves become inflammed and painful. This can lead to post-herpetic neuralgia.