Varicella zoster virus Varicella zoster virus Varicella zoster virus or 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, zoster virus, and human herpesvirus type 3 (HHV-3). VZV infections are species-specific to humans, but can survive in external environments for a few hours, maybe a day or two. VZV multiplies in the lungs, and causes a wide variety of symptoms. After the
WHO disease staging system for HIV infection and disease WHO disease staging system for HIV infection and disease WHO Disease Staging System for HIV Infection and Disease was first produced in 1990 by the World Health Organization and updated in September 2005. It is an approach for use in resource limited settings and is widely used in Africa and Asia and has been a useful research tool in studies of progression to symptomatic HIV disease. Most of these conditions are opportunistic infections that can be easily treated in healthy people. The staging system is different for adults and adolescents and children. Stage I: HIV disease is asymptomatic and not