First Episodes of Norovirus and Sapovirus Gastroenteritis Protect Against Subsequent Episodes in a Nicaraguan Birth Cohort

Norovirus-associated diarrhea and asymptomatic infection in children aged under 4 years: a community-cohort study in the Philippines

Objectives

This study aimed to estimate the incidence of norovirus (NoV)-associated diarrhea and asymptomatic infections in children under 4 years of age and identify the genotypes of multiple NoV infections.

Methods

A community-based cohort study was conducted in Tarlac, Philippines. Children aged 0-2 years were followed up for 2 years. The prevalence and incidence rates of NoV-associated diarrhea and asymptomatic infections were calculated. Risk factors were assessed using the Cox proportional hazards model. The genotypes and immunotypes of repeated infections were tabulated.

Results

A total of 338 children aged 6208 child-months were analyzed. NoV was detected in 17.4% (84 of 527, 95% confidence interval [CI]: 12.7-19.7%) of diarrheal episodes and 10.8% (219 of 2031, 95% CI: 9.4-12.3%) of asymptomatic stool samples. The highest incidence of NoV-associated diarrhea occurred in children aged 6-11 months (2.31 per 100 child-months, 95% CI: 1.30-3.32) and 18-23 months (2.34 per 100 child-months, 95% CI: 1.57-3.12), whereas the highest incidence of asymptomatic NoV infection was observed in children aged 12-23 months (4.49 per 100 child-months, 95% CI: 3.41-5.56). Repeated NoV infections were detected between different genotypes, except in two children who had repeated NoV GI.3 and two children with GI.9 infections.

Conclusions

Children had the highest risk of NoV-associated diarrhea during their first year of life, whereas asymptomatic NoV infections persisted after the second year. Repeated NoV infections suggest genotype-specific immunity after NoV infection.

Viral gastroenteritis

Since the discovery of norovirus in 1972 as a cause of what was contemporarily known as acute infectious non-bacterial gastroenteritis, scientific understanding of the viral gastroenteritides has continued to evolve. It is now recognised that a small number of viruses are the predominant cause of acute gastroenteritis worldwide, in both high-income and low-income settings. Although treatment is still largely restricted to the replacement of fluid and electrolytes, improved diagnostics have allowed attribution of illness, enabling both targeted treatment of individual patients and prioritisation of interventions for populations worldwide. Questions remain regarding specific genetic and immunological factors underlying host susceptibility, and the optimal clinical management of patients who are susceptible to severe or prolonged manifestations of disease. Meanwhile, the worldwide implementation of rotavirus vaccines has led to substantial reductions in morbidity and mortality, and spurred interest in vaccine development to diminish the impact of the most prevalent viruses that are implicated in this syndrome.

Genotypes Diversity of Acute Gastroenteritis Outbreaks Caused by Human Sapovirus - Beijing Municipality, China, 2015-2021

Introduction

Human sapovirus (HuSaV) is an enteric virus responsible for sporadic cases and outbreaks of acute gastroenteritis (AGE) globally. A seven-year active surveillance study was conducted to investigate the molecular epidemiology of HuSaVs associated with AGE outbreaks in Chaoyang District of Beijing Municipality, China from January 2015 to December 2021.

Methods

Fecal and anal swab samples were obtained from patients experiencing AGE outbreaks. HuSaVs were identified through reverse transcription polymerase chain reaction (RT-PCR), and partial viral protein 1 (VP1) sequences (approximately 434 base pairs) were utilized for genotyping, single nucleotide polymorphism (SNP) analysis, and phylogenetic examination.

Results

HuSaVs were identified in 71 AGE outbreaks, demonstrating a detection rate of 10.5%, second only to norovirus. The primary demographic affected by HuSaV were children under the age of 5 in kindergarten settings. Infection rates tended to peak during two distinct periods: May to June and September to December. Upon genotyping, seven distinct genotypes emerged. GII.3 was the most prevalent, accounting for 54.9% of cases, followed by GI.1 (12.7%), GI.2 (9.9%), GII.5 (7.0%), GI.5 (2.8%), GI.6 (1.4%), GII.1 (1.4%), and untyped cases (9.9%). A phylogenetic analysis of GII.3 identified three distinct groups, with 15 notable SNPs observed.

Conclusions

This study offers a comprehensive analysis of the persistent prevalence of HuSaV outbreaks in Chaoyang District, Beijing Municipality, China. Over time, the diversity of HuSaV subtypes has shifted, and it is now recognized as the second leading viral agent responsible for AGE outbreaks. This highlights the importance of ongoing surveillance in the future.

Immunogenicity and tolerability of a bivalent virus-like particle norovirus vaccine candidate in children from 6 months up to 4 years of age: A phase 2 randomized, double-blind trial

We conducted a dose-finding phase 2 study of the HilleVax bivalent virus-like particle (VLP) vaccine candidate (HIL-214) in two cohorts of children, 6-≤12 months and 1-≤4 years of age (N = 120 per cohort), in Panama and Colombia (ClinicalTrials.gov, identifier NCT02153112). On Day 1, children randomized to one of the four equal groups received intramuscular injections of four different HIL-214 formulations containing 15/15, 15/50, 50/50, or 50/150 μg of GI.1/GII.4c genotype VLPs and 0.5 mg Al(OH)₃. On Day 29, half the children in each group received a second vaccination (N = 60), while the other half received saline placebo injections to maintain the blind. VLP-specific ELISA Pan-Ig and histo-blood group binding antigen-blocking antibodies (HBGA) were measured on Days 1, 29, 57 and 210. On Day 29, after one dose, there were large Pan-Ig and HBGA responses in both age cohorts with some indication of dose-dependence, and higher geometric mean titers (GMT) in the older children. A further increase in titers was observed 28 days after a second dose in the 6-≤12-month-old groups, but less so in the 1-≤4-year-old groups; GMTs at Day 57 were broadly similar across doses and in both age groups. GMTs of Pan-Ig and HBGA persisted above baseline up to Day 210. All formulations were well tolerated with mostly mild-to-moderate transient solicited adverse events reported by parents/guardians, and no vaccine-related serious adverse events occurred. Further development of HIL-214 is warranted to protect the most susceptible young children against norovirus.

Sapovirus Infections in an Australian Community-Based Healthy Birth Cohort During the First 2 Years of Life

BACKGROUND

Sapovirus is an important cause of acute gastroenteritis (AGE) in young children. However, knowledge gaps remain in community settings. We investigated the epidemiology, disease characteristics, and healthcare use associated with sapovirus infections in Australian children during their first 2 years of life.

METHODS

Children in the Brisbane-based Observational Research in Childhood Infectious Diseases birth cohort provided daily gastrointestinal symptoms (vomiting/loose stools), weekly stool swabs, and healthcare data until age 2 years. Swabs were batch-tested for sapovirus using real-time polymerase chain reaction assays. Incidence rates and estimates of associations were calculated.

RESULTS

Overall, 158 children returned 11 124 swabs. There were 192 sapovirus infection episodes. The incidence rate in the first 2 years of life was 0.89 infections per child-year (95% confidence interval [CI], .76-1.05), and the symptomatic incidence rate was 0.26 episodes per child-year (95% CI, .17-.37). Age ≥6 months, the fall season, and childcare attendance increased disease incidence significantly. Fifty-four of the 180 (30%) infections with linked symptom diaries were symptomatic, with 72% recording vomiting and 48% diarrhea. Prior infection reduced risk of further infections (adjusted hazard ratio, 0.70 [95% CI, .54-.81]) in the study period. Viral loads were higher and viral shedding duration was longer in symptomatic than asymptomatic children. Twenty-three (43%) symptomatic episodes required healthcare, including 6 emergency department presentations and 2 hospitalizations.

CONCLUSIONS

Sapovirus infections are common in Australian children aged 6-23 months. Efforts to reduce childhood AGE after the global rollout of rotavirus vaccines should include sapovirus where estimates of its incidence in communities will be crucial.