Human alphaherpesvirus 3 (HHV-3), usually referred to as the varicella-zoster virus (VZV), is one of eight herpesviruses known to infect humans. It causes chickenpox (varicella), a disease most commonly affecting children, teens, and young adults, and shingles (herpes zoster) in adults; shingles is rare in children. VZV is a worldwide pathogen known by many names: chickenpox virus, varicella virus, and zoster virus. VZV infections are species-specific to humans, but can survive in external environments for a few hours, maybe a day or two.Primary varicella zoster virus infection results in chickenpox (varicella), which may result in complications including encephalitis, pneumonia(either direct viral pneumonia or secondary bacterial pneumonia), or bronchitis (either viral bronchitis or secondary bacterial bronchitis). Even when clinical symptoms of chickenpox have resolved, VZV remains dormant in the nervous system of the infected person (virus latency), in the trigeminal and dorsal root ganglia. VZV enters through the respiratory system. Having an incubation period of 10–21 days, averaging at 14 days. targeting the skin and peripheral nerve, the period of illness is from 3 to 4 days. 1–2 days before the rashes appear, is when this virus is the most contagious. Some signs and symptoms are vesicles that fill with pus, rupture, and scab before healing. Lesions tend to stay towards the face, throat, and lower back sometimes on the chest and shoulders. Shingles usually stay located around the waist. Within the human body it can be treated by a number of drugs and therapeutic agents including acyclovir for the chicken pox, famciclovir, valaciclovir for the shingles, zoster-immune globulin (ZIG), and vidarabine. VZV immune globulin is also a treatment.Acyclovir is frequently used as the drug of choice in primary VZV infections, and beginning its administration early can significantly shorten the duration of any symptoms. However, reaching an effective serum concentration of acyclovir typically requires intravenous administration, making its use more difficult outside of a hospital.