Epidemiology of norovirus-like illness outbreaks in a large urban health department

Background

Among the Norovirus outbreaks that were reported to the Centers for Disease Control and Prevention (CDC) from July 1997 - June 2000, 57% were foodborne, 16% were person-to-person, 3% were waterborne, and 23% had undetermined transmission. According to the August 2007 MMWR, data suggests that person-to-person transmission accounts for an even larger portion of Norovirus-like outbreaks. Norovirus-like illness accounted for approximately 67% of outbreaks reported by the Cuyahoga County Board of Health (CCBH) in 2007. Of these, 73% were person-to-person transmission and 69% were associated with longterm care, assisted living, or health care facilities.

Methods

CCBH completes the CDC Outbreak Report of Suspected Viral Gastroenteritis form on all reported outbreaks of norovirus-like illness. Outbreaks that involve food operations often incorporate a case-control component in the investigation. Attempts are also made to collect stool specimens from each outbreak Using local surveillance and outbreak data from January 1, 2006 through May 31, 2008, we will characterize epidemiological trends of norovirus-like outbreaks in Cuyahoga County, Ohio (Cleveland, Lakewood, and Shaker Heights excluded) using descriptive statistics.

Results

Results are pending. Outbreak characteristics will include outbreak setting, mode of transmission, number ill, provider visits, hospitalizations, symptom presentation, and seasonal trends.

Discussion

The implementation of a national surveillance system for all acute gastroenteritis outbreaks regardless of mode of transmission may correct a potential surveillance bias. Norovirus outbreaks represent a large portion of outbreaks investigated by local health departments and accurate characterization of these outbreaks will enable local health departments to plan interventions more efficiently.