Molecular and Epidemiological Characteristics of Norovirus Associated with Community-Based Sporadic Gastroenteritis Incidents and Norovirus Outbreaks in Victoria, Australia, 2002–2007

OBJECTIVES: The molecular and epidemiological features of community-based norovirus-associated sporadic gastroenteritis incidents (NASGIs) are poorly understood. This study examined these features and compared the findings with studies of community-based and institutional norovirus-associated gastroenteritis outbreaks (NAGOs). METHODS: Fecal specimens from NASGIs and NAGOs that occurred in Victoria, Australia (2002-2007) were tested for norovirus by reverse transcription-polymerase chain reaction methodology. Norovirus genotype was determined by nucleotide sequence analysis. RESULTS: 106 community-based NASGIs, 116 community-based NAGOs and 902 institutional NAGOs were identified. The mean age and gender ratio of individuals associated with community-based NASGIs and community-based NAGOs were similar but differed from that found for institutional NAGOs. Although GII.4 was the predominant genotype associated with all three incident types, the mix of genotypes was similar for community-based NASGIs and community-based NAGOs but that for institutional NAGOs was different. All three incident types had a similar seasonal periodicity due to the pronounced seasonal periodicity of GII.4 incidents. CONCLUSIONS: The molecular and epidemiological features of noroviruses associated with community-based NASGIs and community-based NAGOs are similar but are different from those found for institutional NAGOs.