Norovirus activity – United States 2006-2007

In late 2006, CDC began receiving requests for information about a perceived increase in the number of outbreaks of acute gastroenteritis (AGE), especially those involving person-to-person transmission in long-term care facilities. No national surveillance system exists for AGE outbreaks, including those caused by norovirus, unless food-borne transmission is suspected. CDC solicited information from the health departments of 24 states who reported a total of 1,316 AGE outbreaks, onset during October-December 2006; a median of 50% occurred in long-term care facilities, and a median of 26% had laboratory confirmation of norovirus by RT-PCR. Of these 24 states, 22 (92%) reported an increase in the number of outbreaks compared with the same period in 2005. Morbidity Mortality Weekly Report 2007;56(33):842-6.