FIG. 3.
Low-dose intraperitoneal or intravenous infections can result in efficient vertical transfer of virus to the fetus by 1 week postinfection. Pregnant female mice were infected intraperitoneally (A) or intravenously (B) 9 or 12 days postconception, respectively, with 2 × 106 PFU of VVWR. Viral titers in the uterus, placenta, and fetuses were determined 7 days postinfection by plaque titration as described in Materials and Methods. The dotted horizontal line indicates the limit of detectability of the plaque assay (120 PFU/g of tissue). The maternal virus titer in the uterus is shown as a solid horizontal line.