Murine cytomegalovirus: reactivation in pregnancy.

Murine cytomegalovirus (MCMV) may be rapidly and reproducibly attenuated by passage in tissue culture. A high proportion of CDI mice neonatally infected with the virulent strain of CMV can be shown to have replicating virus in the kidneys for up to 90 weeks p.i. and this high rate of isolation is not altered in pregnancy. A much lower rate of isolation from the kidneys is seen in CDI mice neonatally infected with the attenuated strain. However, this isolation rate was significantly increased during pregnancy and higher titres of virus were recovered.