“…At the site of entry, which is normally the respiratory tract, these viruses replicate and traffic to the tissues of the kidneys (Heritage et al 1981, McCance 1983) and the central nervous system, where they sustain a long-term infection (Elsner & Dörries 1992, Quinlivan et al 1992. A recurrence of the infection may be induced by significant immunosuppression, as in the case of kidney (Hogan et al 1980, Kahan et al 1980, Gardner et al 1984) and bone marrow transplants (O'Reilly et al 1981, Arthur et al 1988) and other factors such as immunodeficiency diseases, diabetes, other chronic diseases, immunosuppressive chemotherapy, pregnancy ) and old age (Tajima et al 1990). …”