Herpes zoster (Shingles) is a painful vesicular (blistering) eruption of the skin that follows a nerve root pathway.  Shingle is caused by the Varicella-zoster virus.  This is the same virus that causes chicken pox.  Primary infection with this virus develops into chicken pox and reactivation of the virus later causes shingles.  You cannot get shingles without previous chicken pox infection.  After initial infection, the virus goes dormant in the bases of nerves near the spinal column.  Later in life it reactivates ( no one knows why) and causes a painful skin eruption along the path of that nerve.  Depending on the location of eruption, the course and outcome can be very different.

Signs and symptoms

The signs and symptoms of herpes zoster are fairly straight forward.  That is a painful, vesicular rash that occurs on one side of the body only.  It is so one sided that you can essentially draw a line where the rash stops.  Other symptoms are associated that may cloud the diagnosis.  At times there is no rash, only pain.  This can be mistaken for other ailments including:  Kidney stones, muscle strain, or trigeminal neuralgia.  Other systemic symptoms may include headache, fever, fatigue and malaise.

Course of disease

The initial symptom is usually fairly severe pain or itching followed by what is called a papular rash.  This rash develops clusters of blisters (vesicles) after 3-4 days.  In healthy individuals, the rash should crust over in 7-10 days but may take weeks to fully go away.  Affected individuals may be left with scarring, pigment changes and pain for years to come.  While an infected individual cannot transmit the disease to another, they can give a previously unexposed person chicken pox until the lesions crust over.  Zoster that affects the ophthalmic division of the trigeminal nerve are at risk of sight damaging eye involvement.  This area is shown in green.  

Treatment

While there is no treatment, there are things that can limit the disease and alleviate symptoms.  General treatment involves keeping the rash clean and dry to reduce risk of secondary infection.  Creams and ointments usually are not recommended.  The rash should be kept covered while blistering to prevent spread of chicken pox.  If given within 72 hours of the rash eruption, antiviral medications are of use.  The include acyclovir (Zovirax), famciclovir (Famvir), and valacyclovir (Valtrex).  Other treatments include oral pain meds, anti-seizure meds, tricyclic antidepressants and steroid injections.

Prevention

Prevention is more difficult as most people have already been exposed to the varicella zoster virus.  It is estimated that up to 1/3 of the population will develop shingles at some point in their lives.  Progress has been made in the area of prevention with the development of vaccines.  The first vaccine developed was Zostavax, developed and licensed by Merck in 2006.  This was an attenuated live vaccine.  I was never a big fan of this vaccine because it was only about 50% effective initially and the effectiveness waned as time went on and the recipient was older.  It is estimated that the effectiveness dropped to about 35% after 6 years.  Glaxosmithkline came out with Shingrix in 2017.  The was a great improvement.  This vaccine was developed using recombinant DNA technology.  It is estimated to be up to 97% effective and remains at least 85% effective after 4 years.  Shingrix is recommended for ages 50 and over for the prevention of Herpes zoster.  It is recommended as two injections with the second dose 2-6 months after the first.  The most commonly reported reactions to Shingrix include pain at injection site, muscle aches and fatigue.