Introduction
Human rhinoviruses (HRV) are highly prevalent worldwide, causing a significant burden of acute respiratory illness and antibiotic use among young children (1, 2). Molecular techniques have identified HRV types A, B, and C, with over 100 distinct genotypes under the genusEnterovirus (3, 4, 5, 6, 7, 8). Genotypes frequently cocirculate, and infection with one genotype elicits only low or no cross-protection (9), which poses a challenge for HRV vaccine design. Previous studies suggest that predominant genotypes are varied and often transient (5, 10, 11, 12, 13, 14, 15). However, the lack of HRV sequencing in most regions limits our understanding of individual epidemic patterns, including transmission and pathogenicity, and the mechanisms underlying genotype turnover and persistence.
HRVs cocirculate with other respiratory viruses that vary greatly in their structural, genomic, and antigenic properties. Before the emergence of SARS-CoV-2, influenza, respiratory syncytial virus (RSV), parainfluenza viruses 1-4 (HPIV 1–4), and metapneumovirus (HPMV) were among the most commonly reported respiratory viruses across all age groups, with greater disease burden in young children and older adults. Respiratory virus circulation patterns vary by type and subtype with influenza, RSV and HPIV typically causing winter epidemics in temperate regions (16), with less pronounced seasonality in the tropics and subtropics (17). While the genetic diversity and circulation patterns of many respiratory viruses are not well described, HRV and adenoviruses are known to circulate year-round across all climatic regions, with HRV peaks during autumn/winter (18) and adenovirus peaks during winter/spring (19).
Public health and social measures (PHSMs) enacted against COVID-19 substantially changed person-to-person contact patterns, which profoundly affected the epidemiology and evolution of human respiratory viruses. As a result, significant reductions in the circulation of all common respiratory viruses have been reported globally since the pandemic onset (20, 21, 22, 23, 24, 25), and winter epidemics were notably absent in 2020 and 2021. However, intermittent outbreaks of influenza (26), RSV (27), and HRV (23, 28, 29) have occurred in locations where control measures were relaxed intermittently or completely.
In Hong Kong, seasonal influenza circulation began to subside as early as February 2020 due to behaviour changes and the implementation of PHSMs (22), and circulation remained suppressed until COVID-19 control measures were dropped in early-mid 2023 (30, 31). Paediatric hospitalisations associated with respiratory viruses were reduced by 85%–99% in 2020 (23). When schools reopened late in 2020, paediatric hospitalisation rates increased, mainly due to cases of enterovirus/rhinovirus (23). This surge ultimately resulted in the temporary closure of primary and secondary schools in November 2020 (32). To better understand the effects of PHSMs, we characterise the genetic diversity of HRV detected in paediatric cases in Hong Kong between August 2020 – October 2021.