Complicated norovirus infection and assessment of severity by a modified Vesikari disease score system in hospitalized children

BACKGROUND: Norovirus (NoV) GII.4 is the most common genotype for norovirus gastroenteritis worldwide. New variants or subgenotypes are continuously emerging, thus posing a serious threat to child health. METHODS: We compared retrospectively the clinical manifestations and complications of norovirus gastroenteritis in children from April, 2004 through December, 2012. NoV variants were analyzed to investigate the association of circulating viral strains with the complications. A modified disease severity score system based on Vesikari score system was devised and to evaluate disease severity. RESULTS: Compared to the outbreak in 2004/2005 winter, significant higher incidence of complications in the later periods are: convulsive disorder (p < 0.001) in 2006/2007 winter gastrointestinal hemorrhage (p = 0.047) and severe abdominal pain or irritability (p = 0.033) in 2008/09/10 winter; gastrointestinal hemorrhage (p = 0.030), severe abdominal pain or irritability (p = 0.014), and prominent hyperthermia (fever >39 °C, p = 0.001) in 2011/2012 winter. GII.4 Den_Haag_2006b, GII.4 2010, GII.4 Sydney 2012, and GII.4 2012b were the predominant strains in the outbreaks after 2006. By the modified severity score system, severe norovirus disease occurred in 28.5 %, 32 %, 33.3 %, and 30.2 % of the patients in the four periods. A longer duration of hospitalization (p = 0.02) were found in those with high score irrespective of the year of admission. CONCLUSIONS: Our study demonstrated NoV outbreaks in northern Taiwan caused by different GII.4 variants that were associated with specific complications and uncommon clinical presentations. A modified severity score system first proposed in this study was able to identify severe cases with a longer hospital stay in NoV-infected children.