key: cord-0770045-hht0u06l authors: Kuitunen, Ilari; Artama, Miia; Haapanen, Marjut; Renko, Marjo title: Rhinovirus spread in children during the COVID‐19 pandemic despite social restrictions—A nationwide register study in Finland date: 2021-07-11 journal: J Med Virol DOI: 10.1002/jmv.27180 sha: 9e314174af28966cfaed02e6ab348ab4fcbb1f92 doc_id: 770045 cord_uid: hht0u06l Social restrictions during the coronavirus disease 2019 pandemic strongly affected the epidemiology of influenza and respiratory syncytial virus (RSV). As rhinovirus seemed to spread despite the restrictions, we aimed to analyze rhinovirus epidemiology in children during the pandemic. This register‐based study used data from the Finnish Infectious Disease Register. Nationwide rhinovirus findings from July 2015 to March 2021 were included and stratified by age (0–4, 5–9, and 10–14). Cumulative 14‐day incidence per 100000 children was calculated. Four thousand five hundred and seventy six positive rhinovirus findings were included, of which 3788 (82.8%) were among children aged 0–4. The highest recorded incidence was 36.2 among children aged 0–4 in October 2017. The highest recorded incidence during the pandemic period was 13.6 in November 2020. The impact of the restrictions was mostly seen among children aged 0–4 years of age in weeks 14–22 in 2020. The incidence has since remained near reference levels in all age groups. Strict restrictions temporarily interrupted the circulation of rhinovirus in spring 2020. Rhinovirus incidence returned to normal levels soon after the harsh restrictions were lifted. These looser social restrictions prevented RSV and influenza seasons but failed to prevent the spread of rhinovirus. opening seemed to have little impact on detection in children in Finland. 5 A study from Austria demonstrated that the lockdown reduced rhinovirus detections at first, but as soon as the first restrictions were lifted, the spread continued. 6 Reports from Japan and China have confirmed that rhinovirus has spread among school-aged children during the restrictions and despite the use of face masks. 7, 8 In Australia, rhinovirus detections first decreased after lockdown started but later exceeded the incidence of previous years, even though the restrictions were unchanged. 9 Interestingly, another Australian study showed that respiratory syncytial virus (RSV) cases had a high increase after the restrictions were eased. 10 However, this was not seen in Finland, where the RSV season 2020-2021 did not occur despite schools and day care remaining open. 11 The social and traveling restrictions prevented the 2020-2021 influenza season in Finland. 12 With these restrictions Finland has managed to keep the incidence of SARS-CoV-2 as the lowest in Europe during the second and third waves. The aim of this report is to describe the epidemiology of rhinovirus infections in children during the COVID-19 pandemic in Finland. Data for this retrospective register-based surveillance study were gath- infections are asymptomatic and therefore the spreading is difficult to control as asymptomatic carriers are able to spread the virus. 21 Rhinovirus typically causes a mild disease for adults, but for children, it is a common cause of wheezing and asthma exacerbations. 22 Wheezing episodes typically occur for children under 2 years of age, and rhinovirus type C is associated with severe wheezing and febrile infections. 23 Furthermore, rhinovirus as the cause of first severe wheezing has been shown to predict later asthma in children. 24 The strengths of this study are the nationwide infectious disease register, which collects current information on notifiable diseases and is updated daily. All the previous studies that focused on rhinovirus detections during the COVID-19 pandemic have been local or regional studies; thus, we are among the first to present nationwide surveillance results. Furthermore, we were able to analyze agestratified incidence. The main limitation is the lack of testing numbers, as the results might be due to limited testing, and testing rates would enable a test-negativity analysis. However, rhinovirus is tested only as part of respiratory panels, which are used only in pediatric hospitals and emergency departments, and multiplex PCR testing is typically used for patients needing inpatient admission. Therefore, we feel that the current rates are the best possible prediction and present the real incidence of rhinovirus infections evaluated at pediatric hospitals in Finland. Another limitation is that due to the register design we have no information whether the children who Impact of nonpharmaceutical interventions targeted at COVID-19 pandemic on influenza burden-a systematic review COVID-19 and infant hospitalizations for seasonal respiratory virus infections Effect of social distancing due to the COVID-19 pandemic on the incidence of viral respiratory tract infections in children in Finland during early 2020 Physical distancing in schools for SARS-CoV-2 and the resurgence of rhinovirus The impact of the lockdown and the re-opening of schools and day cares on the epidemiology of SARS-CoV-2 and other respiratory infections in children-a nationwide register study in Finland Puchhammer-Stöckl E. 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