Respiratory syncytial virus seasonality in China: implications for intervention
Authors: Lili Ren, Zhongjie Li
Journal: The Lancet Global Health (2024)

Respiratory syncytial virus (RSV) is the leading cause of hospitalisation for acute lower respiratory infections in children younger than 5 years worldwide.1Li Y Wang X Blau DM et al.Global, regional, and national disease burden estimates of acute lower respiratory infections due to respiratory syncytial virus in children younger than 5 years in 2019: a systematic analysis.Lancet. 2022; 399: 2047-2064Summary Full Text Full Text PDF PubMed Google Scholar Infants in their first 6 months of life and children in low-income and middle-income countries are disproportionately affected.1Li Y Wang X Blau DM et al.Global, regional, and national disease burden estimates of acute lower respiratory infections due to respiratory syncytial virus in children younger than 5 years in 2019: a systematic analysis.Lancet. 2022; 399: 2047-2064Summary Full Text Full Text PDF PubMed Google Scholar The approval of two RSV vaccines (the Arexvy vaccine in older individuals, and the Abrysvo vaccine in older individuals and pregnant women) and one long-acting monoclonal antibody (nirsevimab) by the US Food and Drug Administration and the European Medicines Agency has provided valuable tools for averting RSV-associated disease burden.2Progress at last against RSV.Nat Med. 2023; 292143Google Scholar In December, 2023, the National Medical Products Administration of China also approved its first RSV preventive product (nirsevimab), marking this event a key milestone in the prevention of RSV infections in China. Passive immunoprophylaxis, including maternal vaccination and monoclonal antibody injections, is fast and direct in effect, but it only lasts for a limited period of 5–6 months.3Kampmann B Madhi SA Munjal I et al.Bivalent prefusion F vaccine in pregnancy to prevent RSV illness in infants.N Engl J Med. 2023; 388: 1451-1464Crossref PubMed Scopus (176) Google Scholar, 4Hammitt LL Dagan R Yuan Y et al.Nirsevimab for prevention of RSV in healthy late-preterm and term infants.N Engl J Med. 2022; 386: 837-846Crossref PubMed Scopus (304) Google Scholar The efficiency of RSV vaccination and passive immunoprophylaxis on disease control therefore largely depends on strategies for implementation, with regard to how and when they are used. In addressing the prevention and control of RSV in China and globally, it is crucial to elucidate the regional seasonality of RSV and to develop specific regional vaccination strategies within countries. Globally, the epidemic profile of RSV shows distinct seasonal patterns, with the majority of RSV illness typically occurring in winter and early spring in temperate regions, in the rainy season in some tropical regions, and year-round in other tropical regions.6Obando-Pacheco P Justicia-Grande AJ Rivero-Calle I et al.Respiratory syncytial virus seasonality: a global overview.J Infect Dis. 2018; 217: 1356-1364Crossref PubMed Scopus (231) Google Scholar China currently does not have nationwide data on RSV epidemiological features, with most of the available information stemming from studies within specific regions over brief periods or from ongoing research in some areas over a sustained duration. In The Lancet Global Health, Ling Guo and colleagues have reported a systematic analysis that describes the seasonal epidemic patterns of RSV in China.5Guo L Deng S Sun S Wang X Li Y Respiratory syncytial virus seasonality, transmission zones, and implications for seasonal prevention strategy in China: a systematic analysis.Lancet Glob Health. 2024; (published online April 23.)https://doi.org/10.1016/S2214-109X(24)00090-1Google Scholar The authors also provide an in-depth assessment of the potential applicability of seasonal RSV immunisation programmes for different regions in China. They identified specific patterns of RSV seasonality in a refined way, defining two distinct patterns of seasonality (clear and stable; or unclear and unstable) among 21 provinces. The authors also delineated four RSV transmission zones, defined as groups of provinces with similar RSV seasonality. Such findings provide the fundamental data for the development of refined immunisation strategies. This proposed concept of seasonal transmission zones of infectious diseases will have an important impact on the prevention and control of RSV. There are several barriers to effective implementation of RSV prevention strategies in China. Firstly, Guo and colleagues found that 11 of 34 provincial administrative regions have no RSV epidemic data, emphasising the importance of establishing RSV surveillance at both the national and subnational levels in China. A dedicated RSV surveillance system would help to fill the data gaps in these regions, evaluate the effectiveness of interventions, and monitor the evolution of the virus in the future. WHO has been developing a global RSV monitoring system, to be used as a tool to lessen the disease burden attributed to RSV.7WHOWHO technical meeting on piloting RSV surveillance based on the Global Influenza Surveillance and Response System.https://iris.who.int/bitstream/handle/10665/252617/WHO-OHE-PED-GIP-2016.6-eng.pdf?sequence=1Date: 2016Date accessed: March 10, 2024Google Scholar Therefore, it is essential for China to establish a national RSV monitoring system and to conduct continuous research, which will contribute to tracing the dynamics of RSV, either in clear and stable or unclear and unstable patterns, and potentially identify the influencing factors that lead to unstable epidemics. Secondly, current research on the epidemiological characteristics of RSV in China primarily relies on hospital cases, and the recording of RSV cases in hospital surveillance systems is mainly based on influenza-like illness characteristics. This discrepancy in the studied population might affect the identification of RSV epidemic features, thus necessitating the establishment of a comprehensive case definition for RSV surveillance or research on disease burden. Thirdly, previous studies have indicated that the transmission of RSV antigenic subgroups is associated with RSV epidemics.8Bimouhen A Regragui Z El Falaki F et al.Circulation patterns and molecular epidemiology of human respiratory syncytial virus over five consecutive seasons in Morocco.Influenza Other Respir Viruses. 2023; 17e13203Crossref Scopus (1) Google Scholar Expansion of virological monitoring to differentiate virus types and identify genetic groups has been recommended by WHO,9WHOWHO strategy for global respiratory syncytial virus surveillance project based on the influenza platform.https://www.who.int/publications/i/item/who-strategy-for-global-respiratory-syncytial-virus-surveillance-project-based-on-the-influenza-platformDate: 2019Date accessed: March 10, 2024Google Scholar which could facilitate optimisation of the timing of seasonal immunisation against RSV in accordance with the fluctuating patterns of RSV epidemics, by intensifying research on RSV genotypes during surveillance. Lastly, it is imperative to consider the state of health-care infrastructure in different regions of China when developing RSV preventive delivery strategies. Policies should be assessed and improved on in view of local socioeconomic considerations and the population-level benefit of reducing RSV-associated disease burden. We declare no competing interests. Respiratory syncytial virus seasonality, transmission zones, and implications for seasonal prevention strategy in China: a systematic analysisAlthough substantial variations in RSV seasonality were observed across provinces of China, our study identified distinct transmission zones with shared RSV circulating patterns. These findings could have important implications for decision making on RSV passive immunisation strategy. Furthermore, the methodological framework in this study for defining RSV seasons and identifying RSV transmission zones is potentially applicable to other countries or regions. Full-Text PDF Open Access