Multisystem inflammatory syndrome in children during the first two years of the COVID-19 pandemic in Luxembourg

Objective

Estimate the incidence of multisystem inflammatory syndrome (MIS-C) in children (0-15 years), the role of SARS-CoV-2 variants during the first two years of COVID-19 pandemic in Luxembourg; and describe the demographic, biological and clinical characteristics of the patients.

Method

Observational retrospective cohort study. Cases between March 2020 and February 2022 were ascertained from the national registry of MIS-C cases by a retrospective review of medical records. Reported SARS-CoV-2 infections were obtained from the national COVID-19 surveillance system. We calculated monthly MIS-C incidence, the ratio between MIS-C and SARS-CoV-2 infections and associated rate ratios by the periods corresponding to the circulation of different variants.

Results

18 children were diagnosed with MIS-C among 35,200 reported infections. The incidence rate of MIS-C was 7.2 [95% confidence interval (CI) 4.5-11.4] per 1,000,000 person-months. A higher incidence of MIS-C was observed between September and December 2021, corresponding to the circulation of the Delta variant than during the first year of the pandemic (RR 3.6, 95% CI, 1.1-12.3). The lowest rate of MIS-C per infection was observed during the Omicron (RR 0.17, 95% CI, 0.03-0.82). Median age at diagnosis was 6.5 years. Previously healthy children made up 88% of MIS-C cases, none were vaccinated against SARS-CoV-2. 33% required intensive care. All patients recovered fully.

Conclusions

MIS-C incidence and MIS-C risk per infection changed significantly over time during the first two years of COVID-19 pandemic. Monitoring of MIS-C incidence in future SARS-CoV-2 waves will be essential to guide public health interventions and vaccination policies for children.

Hepatitis E virus: Whole genome sequencing as a new tool for understanding HEV epidemiology and phenotypes

Hepatitis E Virus (HEV) is emerging as a public health concern across Europe and tools for complete genome data to aid epidemiological and virulence analysis are needed. The high sequence heterogeneity observed amongst HEV genotypes has restricted most analyses to subgenomic regions using PCR-based methods, which can be unreliable due to poor primer homology. We designed a panel of custom-designed RNA probes complementary to all published HEV full genome NCBI sequences. A target enrichment protocol was performed according to the NimbleGen® standard protocol for Illumina® library preparation. Optimisation of this protocol was performed using 40 HEV RNA-positive serum samples and the World Health Organization International Reference Panel for Hepatitis E Virus RNA Genotypes for Nucleic Acid Amplification Technique (NAT)-Based Assays and related reference materials. Deep sequencing using this target enrichment protocol resulted in whole genome consensus sequences from samples with a viral load range of 1.25 × 10⁴-1.17 × 10⁷ IU/mL. Phylogenetic analysis of these sequences recapitulated and extended the partial genome results obtained from genotyping by Sanger sequencing (genotype 1, ten samples and genotype 3, 30 samples). The protocol is highly adaptable to automation and could be used to sequence full genomes of large sample numbers. A more comprehensive understanding of hepatitis E virus transmission, epidemiology and viral phenotype prediction supported by an efficient method of sequencing the whole viral genome will facilitate public health initiatives to reduce the prevalence and mitigate the harm of HEV infection in Europe.