The incidence of infectious diseases and viruses other than SARS-CoV-2 amongst hospitalised children in Oslo, Norway during the Covid-19 pandemic 2020-2021.

Background: Measures to reduce spread of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) during the Covid-19 pandemic 2020-2021 may impact other microbiological agents. We aimed to investigate the incidence of infectious diseases and the incidence of viruses other than SARS-CoV-2 amongst children at The Department of Paediatric and Adolescent Medicine, Oslo University Hospital, Norway during 2020-2021 compared to previous years.

Methods: Data from April 1st 2020 - March 31st 2021 were compared to data from corresponding 12-months periods 2017-2020. ICD-10 infectious disease diagnoses were collected from the Hospital Diagnosis and Procedure Registry and results of virus PCR analyses of different specimens (mainly nasopharyngeal (NF) and faecal samples) were collected from the Laboratory System at the Department of Microbiology.

Results: The number of hospital contacts with acute bronchiolitis, viral pneumonia, gastroenteritis and viral central nervous system infections were reduced by 90% (<0.0001), 89% (<0.0001), 74% (<0.0001) and 78% (<0.01), respectively. Respiratory syncytial virus (RSV), influenza virus A and B and Human metapneumovirus (HMPV) were almost completely absent during the pandemic period. The proportions of rhinovirus positive NF samples were 31.7% vs. 34.9% (<0.05), but not significantly different for adenovirus. The proportions of positive faecal samples were 1% vs. 10% for adenovirus (<0.00001) and 3.3% vs. 12% for norovirus (<0.00001), but not significantly different for rotavirus. The proportions of enterovirus positive samples were 3.5% vs. 21.6% (<0.00001).

Conclusion: The incidence of several paediatric infectious diseases mainly of viral aetiology declined significantly during the Covid-19 pandemic. Some common respiratory viruses were almost completely absent.