Measures against SARS-CoV-2 in Sweden were more efficient against rhinovirus infections in older adults than in children: a molecular epidemiology perspective.

Background: Acute respiratory infections (ARIs) are a major global health concern, particularly for children and the elderly. Although rhinoviruses are the primary pathogens causing ARIs, their epidemiology during reduced population mobility and behavioral changes is not well understood. This study aimed to assess whether the Swedish COVID-19 measures changed the epidemiology of Rhinovirus and ARI-causing viruses other than SARS-CoV-2 in the western part of Sweden in 2020.

Methods: A total of 13,791 nasopharyngeal samples from ARI-patients were analyzed for 19 different viruses and bacteria by qPCR. Of the 3,607 samples positive for any virus, 2,018 were positive for rhinovirus (RV) and enterovirus (EV), and 106 contained adenoviruses. Among the EV/RV reactive samples, 249 strains were typed using partial sequencing of 5'UTR and 204 by VP1 or VP4-VP2.

Results: After week 12 when the interventions were implemented, most of the ARI-causing viruses were EV/RV and adenoviruses, besides SARS-CoV-2. In September-October 2020, an outbreak caused by RV-A strains predominantly infected children younger than 13 years and individuals within the age range of their parents. RV-A strains were identified in 118 of 242 (49%) RV-positive samples, followed by RV-C (36%) and RV-B (10%). Before the first wave of SARS-CoV-2, a RV-C outbreak affected all age groups.

Conclusions: This study shows that the moderate Swedish interventions against SARS-CoV-2 were more effective against the spread of ARI-causing virus among adults over 56 years than among young children. These results suggest the need for new strategies for preventing the spread of ARI pathogens like RV and EV, which cause disease in all age groups and can lead to large outbreaks.