<prompt> A patient is suffering from painful vesicular eruption at T-4 dermatome. The cause is:EBV infectionHerpes zosterCMV infectionHerpes simplex  <response>: Refer: Fitz Patricks Dermatology in General Medicine, 7th edition, pg no: 2383-2393Herpes zoster re-activationVaricella zoster virus VZV is the etiology of varicella chickenpox and herpes zoster shingles.Herpes zoster represents reactivation of latent varicella infection and develops in approximately 20 of healthy adults and 50 of immunocompromised persons.IP ranges from 11 to 20 daysVaricella is extremely contagious, with 80-90 of susceptible household contacts developing clinical infectionHerpes zoster classically is a disease of adulthood that affects those older than 50 years of age more severely, it is common in younger persons who had primary varicella infection within the first year of life.Herpes zoster appears upon reactivation of VZV, which may occur spontaneously or may be induced by stress, fever, radiation therapy, tissue damage i.e., trauma or immunosuppression.During a herpes zoster infection, the virus continues to replicate in the affected dorsal root ganglion and produces a painful ganglionitis.Inflammation and neuronal necrosis can result in a severe neuralgia that intensifies as the virus spreads down the sensory nerve.Diagnosis and PathologyClinical history and the physical examinationTzanck smear andor a DFA direct fluorescent antibodyViral culture, Serology and PCRTreatment 