Norovirus activity--United States, 2002.

During June-December 2002, an increased number of outbreaks of acute gastroenteritis (AGE) were reported on cruise ships sailing into U.S. ports. In addition, since October 2002, several states have noted an increase in outbreaks of AGE consistent clinically and epidemiologically with norovirus infection, particularly in institutional settings such as nursing homes (CDC, unpublished data, 2002). This report describes recent norovirus activity in two states and New York City (NYC) and data from CDC that indicate the possible emergence of a predominant, circulating norovirus strain.