The predominant clinical manifestations of rotaviral gastroenteritis result from intestinal infection [20-23]. The first day after exposure, the virus infects enterocytes within the villous epithelium of the jejunum and ileum, leading to destruction of the cells of this layer. Destruction of enterocytes results in a transudation of fluid into the intestinal lumen and net loss of fluid and salt in feces. During days two to five after infection, adjacent villi fuse, reducing the surface area of injury and improving integrity of the barrier against fluid loss. From days 6 to 10 after infection, normal villous architecture is restored.
Intestinal injuries lead to a loss of the ability to digest food (especially complex sugars) and to absorb digested food across the intestinal mucosa. This inability to digest complex sugars manifests as transient lactose intolerance.
In addition, rotaviruses may cause secretory diarrhea via the nonstructural glycoprotein (NSP4) enterotoxin, which alters intracellular Ca+2 mobilization in GI epithelial cells [24,25]. Elevation of ionized Ca+2 leads to age-dependent halide ion movement across the plasma membrane. Altered Ca+2 mobilization may signal other Ca+2-sensitive cellular processes, such as cation channels and ion and solute transporters to increase fluid secretion while curtailing fluid absorption [26]. These primary Ca+2-dependent steps appear to be cyclic nucleotide-independent. A secondary component appears to involve the enteric nervous system and may be cyclic nucleotide-dependent [27].