Introduction
Despite vaccine availability, rotavirus persists as a leading cause of gastroenteritis in children under five years of age, and continued surveillance of circulating genotypes is needed to monitor their evolution.
Methods
We collected 8024 rotavirus positive samples throughout Belgium between 2009 and 2023. For 6352 samples we were able to determine the G and/or P genotypes through sequencing of the genes encoding the outer capsid proteins VP7 and VP4.
Results
In the pre-pandemic period, we received an average of 622 samples per season, which decreased to 114 and 111 samples during the two pandemic seasons. In the first post-pandemic season we observed a peak surge of 1048 samples. Notably, the proportion of cases in the 2-5-year-old age group increased from 20.3% before the pandemic to 33% after the pandemic (p<0.001). Over the 14-year study period, the most common genotypes were G2P[4], G3P[8], and G9P[8]. Post-pandemic data show an unusually strong dominance of the “equine-like G3P[8]” genotype in two consecutive seasons (2021-2023). These equine-like G3P[8] strains are strongly associated with the DS-1-like genotype constellation and were first identified in 2014-2015 in Belgium. Additionally, a significant overrepresentation of vaccinated individuals was found within the equine-like VP7 carrying G3P[8]-infected patient samples compared to infections with other genotypes, including typical human VP7 G3P[8].
Conclusion
Despite the presence of typical seasonal genotype fluctuations, the pandemic seems to be associated with several epidemiological changes, including the unusually strong dominance of an emerging rotavirus strain, against which currently used vaccines may be less effective. It is important to continue close monitoring of this strain to investigate whether this is a temporary phenomenon or if these strains may pose an increased public health threat.