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Rotavirus epidemiology, genotypes, and changes during the COVID-19 pandemic in an unvaccinated population, Denmark
Mona Katrine Alberthe Holm1, Sofie Elisabeth Midgley1, Jørgen Engberg2
1Virology & Microbiological Preparedness, Statens Serum Institut, Artillerivej 5, Copenhagen S, 2300, Denmark.
Objectives:
Rotavirus is a major cause of gastroenteritis in children worldwide. Denmark has no routine rotavirus vaccination programme. We aimed to describe national trends in rotavirus epidemiology and genotype distribution from 2014 to 2024, including changes during and after the COVID-19 pandemic.
Methods:
Data on all diagnostic rotavirus analyses performed in Denmark between 2014 and 2024 were obtained from the Danish Microbiology Database. A subset of rotavirus-positive samples was submitted to the national reference laboratory for genotyping and linked with epidemiological data.
Results:
A total of 18,246 rotavirus episodes were identified, and 1800 samples were selected for genotyping. The number of episodes declined during the COVID-19 restrictions in 2020-2021, followed by a substantial increase in 2022. The median age of infected patients increased from 20 to 27 months before the pandemic to 32 months in 2022. Test positivity returned to pre-pandemic levels in 2023-2024, whereas incidence remained elevated. Genotype distribution shifted over time, with G1P[8] dominating in 2014-2015, G3P[8] in 2016-2017 and 2022-2024, and G9P[8] in 2019-2021. Reinfections were uncommon.
Conclusions:
Rotavirus epidemiology in Denmark changed substantially during and after the COVID-19 pandemic, with changes in disease incidence, age distribution, and circulating genotypes. Continued surveillance remains important to monitor epidemiological trends.