Pathophysiology
Clinical meaning
Rotavirus is a non-enveloped, icosahedral, double-stranded RNA virus with a segmented genome (11 segments) encoding 6 structural proteins (VP1-VP4, VP6, VP7) and 6 nonstructural proteins (NSP1-NSP6). The triple-layered particle structure provides extraordinary environmental stability, enabling survival on surfaces for weeks and resistance to many disinfectants. VP4 (P-type) and VP7 (G-type) are the outer capsid proteins that determine serotype and are the primary targets of neutralizing antibodies. The virus attaches to sialylated glycoproteins and integrins on the apical surface of mature villous enterocytes in the jejunum and ileum. Following receptor-mediated endocytosis and uncoating, viral replication occurs in the cytoplasm. The virus preferentially infects mature absorptive enterocytes at the villous tips while sparing the immature secretory crypt cells. This selective tropism results in villous blunting, loss of absorptive surface area, and replacement with immature cells lacking brush border enzymes. The diarrheal mechanism involves at least four interconnected pathways. First, the osmotic component: destruction of mature enterocytes eliminates brush border disaccharidases, particularly lactase, sucrase-isomaltase, and maltase-glucoamylase. Undigested disaccharides (especially lactose) remain in the intestinal lumen, creating an osmotic gradient that draws water and...