Varicella zoster virus (VZV) is a virus that causes chickenpox and shingles in non-immunized persons. VZV is highly infectious and is transmitted by contact with fluid from infected individuals' ruptured blisters or respiratory secretions. Immunity post-infection is usually lifelong though the latent virus inhabits the sensory nerve ganglia, where it can reactivate, causing shingles when immunity declines with aging. Detection of specific IgM antibodies is evidence of a current or recent infection. A demonstration of specific IgG to the bacteria is evidence of past infection.