Disease the time between infection and the appearance of symptoms. The latency period is the time between infection and the ability of the disease to spread to another person, which may precede, follow, or be simultaneous with the appearance of symptoms. Some viruses also exhibit a dormant phase, called viral latency, in which the virus hides in the body in an inactive state. For example, varicella zoster virus causes chickenpox in the acute phase; after recovery from chickenpox, the virus may remain dormant in nerve cells for many years, and later cause herpes zoster (shingles). Diseases may be classified by cause,
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