Potential and postulated routes of entry for CMV infection in the VLBW premature infant. Possible routes of entry include trans-olfactory (Panel A), trans-mucosal in the oropharynx and/or nasopharynx (Panel B), and trans-jejunal via intestinal epithelial cells, Peyer’s patches, or M-cells (Panel C). These routes of entry are not mutually exclusive. The trans-olfactory route has been identified in murine models25 but not validated in human infants. Unresolved questions include whether cell-free or cell-associated virus in milk is infectious. It is presumed that viremia ensues irrespective of the route(s) involved, followed by salivary gland seeding and establishment of latent/persistent infection