Comparison of primers for the detection of genogroup II noroviruses in India

Multiple norovirus infections in a birth cohort in a Peruvian Periurban community

BACKGROUND

Human noroviruses are among the most common enteropathogens globally, and are a leading cause of infant diarrhea in developing countries. However, data measuring the impact of norovirus at the community level are sparse.

METHODS

We followed a birth cohort of children to estimate norovirus infection and diarrhea incidence in a Peruvian community. Stool samples from diarrheal episodes and randomly selected nondiarrheal samples were tested by polymerase chain reaction for norovirus genogroup and genotype. Excretion duration and rotavirus coinfection were evaluated in a subset of episodes.

RESULTS

Two hundred twenty and 189 children were followed to 1 and 2 years of age, respectively. By 1 year, 80% (95% confidence interval [CI], 75%-85%) experienced at least 1 norovirus infection and by 2 years, 71% (95% CI, 65%-77%) had at least 1 episode of norovirus-associated diarrhea. Genogroup II (GII) infections were 3 times more frequent than genogroup 1 (GI) infections. Eighteen genotypes were found; GII genotype 4 accounted for 41%. Median excretion duration was 34.5 days for GII vs 8.5 days for GI infection (P = .0006). Repeat infections by the same genogroup were common, but repeat infections by the same genotype were rare. Mean length-for-age z score at 12 months was lower among children with prior norovirus infection compared to uninfected children (coefficient: -0.33 [95% CI, -.65 to -.01]; P = .04); the effect persisted at 24 months.

CONCLUSIONS

Norovirus infection occurs early in life and children experience serial infections with multiple genotypes, suggesting genotype-specific immunity. An effective vaccine would have a substantial impact on morbidity, but may need to target multiple genotypes.

Norovirus genogroup II gastroenteritis in hospitalized children in South India

The distribution of norovirus (NoV) genogroup II in children < 5 years of age admitted to a south Indian hospital with diarrhea was investigated. Viral RNA extracted from 282 stool samples were screened for NoV GII and positive amplicons sequenced. Twenty-eight (9.9%) had NoV GII infection with a median age of 6 months, with more severe episodes of diarrhea among infected (median Vesikari score 13, interquartile range [IQR] 10-15) than children without infection (median score 10, IQR 8-13, P = 0.002). The study documents NoV GII infections as an important cause of gastroenteritis and the genetic diversity of circulating strains.