Introduction
During the COVID-19 pandemic, a virological anomaly that garnered attention was the persistent global prevalence of rhinoviruses (RV). The non-pharmaceutical interventions implemented to mitigate SARS-CoV-2 transmission—such as mask-wearing, social distancing, and lockdowns—resulted in a substantial reduction in the incidence of respiratory viruses, including influenza, parainfluenza, respiratory syncytial virus (RSV), and human metapneumovirus (hMPV)[1, 2]. However, in notable contradistinction, RV demonstrated adaptability and appeared to coexist with SARS-CoV-2 at a rate consistent with its typical seasonal patterns, despite the decrease in interpersonal contacts due to these public health measures[3]. RV is renowned for its efficient transmission through both airborne particles and fomites. As non-enveloped viruses, rhinoviruses exhibit prolonged survivability on surfaces and resistance to disinfectants containing alcohol, facilitating effective fomite transmission[4-6]. This characteristic likely played a pivotal role in the sustained propagation of RV within populations, even in the face of various pandemic measures such as masking, social distancing, and lockdowns.
RV, commonly known as the ”common cold virus,” has historically been overlooked as a causative agent of severe illness[7]. Nevertheless, in recent years, the clinical significance of RV has garnered considerable attention. Beyond causing common colds, RV infections manifest in a spectrum of clinical outcomes, ranging from asymptomatic infections to severe lower respiratory conditions, including bronchiolitis, pneumonia, and asthma exacerbations[8-10]. The diverse clinical presentations of RV infections indicate a potential association between illness severity and various host and environmental factors[11]. Additionally, factors intrinsic to the virus may influence the transition from asymptomatic infection to severe illness. However, the complexity of this research is compounded by RV’s status as the most diverse virus family within the enterovirus genera. The current RV classification encompasses three species (RV-A, RV-B, and RV-C), further divided into 169 subtypes[12]. Identifying the most clinically relevant subtypes within this diversity is crucial for developing targeted therapeutic strategies against this virus. Despite concerted efforts, establishing meaningful connections between RV species as well as subtypes and symptoms, seasonal patterns, severity, and interactions with other viruses has proven challenging.
Following the extensive COVID-19 epidemic in February 2020, China transitioned into a phase of normalized prevention and control measures starting in May 2020[13]. Responding to the heightened transmissibility of the Delta variant, China implemented a novel strategy termed ”Dynamic COVID-zero” in August 2021. This strategic approach encapsulates China’s accumulated knowledge in effectively managing the Delta variant spread, aiming to control the epidemic with heightened efficiency, reduced cost, and in a shorter timeframe[14]. The core of this strategy lies in the precise implementation of comprehensive measures to address localized COVID-19 cases, swiftly sever the transmission chain, and promptly terminate the epidemic[15].
However, in response to the emergence of the SARS-CoV-2 Omicron subvariants, characterized by attenuated pathogenicity, coupled with the broadening vaccination coverage, these stringent policies were lifted on December 7, 2022. The abrupt shift in Non-Pharmaceutical Interventions (NPIs), combined with the accrued ’immunity debt’ and viral evolution, potentially contributed to the resurgence of other respiratory viruses[16]. Notably, an outbreak of influenza A virus among children was documented following the conclusion of the zero-COVID policy in Shanghai, China[17]. Previous research has indicated that viral interference among influenza virus, rhinovirus, and other respiratory viruses can influence viral infections at both the individual and population levels[18]. Hence, it becomes essential to closely monitor the alterations in the pattern of RV infections post the ending of the zero-COVID policy.
This study investigates epidemiological shifts in RV infections among children on Hainan Islands, with a focus on the periods before and after the termination of the zero-COVID policy. Hainan, a tropical island located at China’s southernmost tip, is known for its warm temperatures, high humidity, and status as a major free trade port and tourist destination. These unique climatic and geographical attributes potentially present distinct health challenges. Specifically, the research provides insights into how policy changes, notably the ending of the zero-COVID policy, influenced the dynamics of respiratory viruses from 2021 to 2023. The aim of this investigation is to enhance our comprehension of RV circulation and associated diseases.