It appears that a nested set of 3' subgenomic transcripts code for the remaining proteins, most notable of which is the capsid protein. In Norwalk viral gastroenteritis the tips of the villi in the intestinal jejunum slough off. There is infiltration of mononuclear cells and polymorphs, but the gastric mucosa remains histologically intact. Transient malabsorbtion and delayed gastric emptying soon follow. The illness usually runs its course in about 1-2 days.
Acquired immunity is poor, lasting a year or so at best.
Prevention Prevention requires a concerted effort to improve sanitation and hygiene standards within any community. Thus many outbreaks can be prevented by enforcing sanitation standards that apply to the preparation and supply of food for public consumption, for many epidemics start at the hands of an ill food handler. Interestingly, however, nearly half of all the Norwalk outbreaks investigated by the Center for Disease Control have been traced back to shellfish that was served raw or undercooked. Shellfish are notorious for concentrating viruses in fecally contaminated waters. Thorough cooking of food is a very good means of preventing viral transmission.