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.