Roughly half of sporadic pediatric acute gastroenteritis (AGE) cases in a single county in Tennessee were caused by GII.4 norovirus, according to data published in Clinical Infectious Diseases. Children with GII.4 norovirus infection also had more severe symptoms and required more medical care.
Norovirus is a leading cause of epidemic AGE in the United States. Most outbreaks occur in winter and are caused by GII.4 noroviruses. Whether this is true of sporadic medically-attended AGE remained unclear. Investigators therefore sought to compare the clinical characteristics and seasonality of GII.4 vs non-GII.4 viruses in children presenting with vomiting and/or diarrhea.
Study patients were recruited from the outpatient, emergency department, and inpatient settings at Vanderbilt Children’s Hospital in Nashville, Tennessee, from December 2012 to November 2015. A total of 3705 children, aged 15 days to 17 years, with AGE symptoms were enrolled and provided stool samples. Quantitative reverse transcription polymerase chain reaction tests for GI and GII noroviruses, and subsequent genotyping by sequencing a partial region of the capsid gene, was completed for 78% of samples.
Overall, 22% of tested samples were norovirus positive. Of these positive samples, 89% were GII positive, 61% were GI positive, and 1% had mixed GI/GII infections. Among the GII-positive samples, 51% were typed as GII.4, and 49% were typed as non-GII.4. When children with GII.4 infections were compared with those with non-GII.4 infections, investigators found that GII.4 infections occurred in younger patients who were more likely to have diarrhea and receive oral rehydration fluids. Investigators did note the presence of norovirus infections throughout the year, but infections peaked in winter.
Study limitations included the use of a single center, which reduces the generalizability of the results, and the inability to genotype all samples. A strength of this study, however, is the inclusion of patients from 3 different clinical settings, which generates a more representative sample of children with medically attended AGE. This also accounts for the potential differences in severity, causative agents, and variable management in different clinical settings. They also noted that due to the large sample size, “we were able to note significant clinical and demographic differences among norovirus genotypes.”
“GII.4 norovirus was consistently the most common genotype in children presenting with AGE and caused a more severe illness,” the researchers concluded. “Seasonal variations were noticed among different genotypes. These data might help in strain selection for candidate norovirus vaccines and also highlight the importance of continuous surveillance…in different geographic regions for vaccine formulation.”
Haddadin Z, Batarseh E, Hamdan L, et al. Characteristics of GII.4 norovirus versus other genotypes in sporadic pediatric infections in Davidson County, Tennessee, USA. [published online July 15, 2020]. Clin Infect Dis. doi: 10.1093/cid/ciaa1001.