Immunology of postviral fatigue syndrome.

Postviral fatigue syndrome is associated with persistent infection by a virus. The patient with the condition has failed to eliminate the virus in the usual time. There is little evidence of a deficient immune response by the patient as the explanation for the viral persistence, and it must be assumed that most of the explanation lies in down-regulation of virus expression in infected cells. The general symptomatology of postinfectious syndromes may be mediated by cytokines liberated as part of the infection. Part of the syndrome may also be due to local effects of virus infection in muscles or the central nervous system (CNS).