regional based within year seasonal variations in influenza related health outcomes CORD-Papers-2022-06-02 (Version 1)

Title: Regional-based within-year seasonal variations in influenza-related health outcomes across mainland China: a systematic review and spatio-temporal analysis
Abstract: BACKGROUND: China experiences large variations in influenza seasonal activity. We aim to update and improve the current understanding of regional-based within-year variations of influenza activity across mainland China to provide evidence for the planning and optimisation of healthcare strategies. METHODS: We conducted a systematic review and spatio-temporal meta-analysis to assess regional-based within-year variations of ILI outpatient consultation rates influenza test positivity rates amongst both ILI outpatients and SARI inpatients and influenza-associated excess mortality rates. We searched English and Chinese databases for articles reporting time-series data on the four influenza-related outcomes at the sub-national and sub-annual level. After synthesising the data we reported on the mean monthly rate epidemic onset duration peak and intensity. RESULTS: We included 247 (7.7%) eligible studies in the analysis. We found within-year influenza patterns to vary across mainland China in relation to latitude and geographic location. High-latitude provinces were characterised by having short and intense annual winter epidemics whilst most mid-latitude and low-latitude provinces experience semi-annual epidemics or year-round activity. Subtype activity varied across the country with A/H1N1pdm09 and influenza B occurring predominantly in the winter whereas A/H3N2 activity exhibited a latitudinal divide with high-latitude regions experiencing a winter peak whilst mid and low-latitude regions experienced a summer epidemic. Epidemic onsets and peaks also varied occurring first in the north and later in the southeast. We found positive associations between all influenza health outcomes. In addition seasonal patterns at the prefecture and county-level broadly resembled their wider province. CONCLUSIONS: This is the first systematic review to simultaneously examine the seasonal variation of multiple influenza-related health outcomes at multiple spatial scales across mainland China. The seasonality information provided here has important implications for the planning and optimisation of immunisation programmes and healthcare provision supporting the need for regional-based approaches to address variations in local epidemiology. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12916-022-02269-5.
Published: 2022-02-10
Journal: BMC Med
DOI: 10.1186/s12916-022-02269-5
DOI_URL: http://doi.org/10.1186/s12916-022-02269-5
Author Name: Diamond Charlie
Author link: https://covid19-data.nist.gov/pid/rest/local/author/diamond_charlie
Author Name: Gong Hui
Author link: https://covid19-data.nist.gov/pid/rest/local/author/gong_hui
Author Name: Sun Fiona Yueqian
Author link: https://covid19-data.nist.gov/pid/rest/local/author/sun_fiona_yueqian
Author Name: Liu Yang
Author link: https://covid19-data.nist.gov/pid/rest/local/author/liu_yang
Author Name: Quilty Billy J
Author link: https://covid19-data.nist.gov/pid/rest/local/author/quilty_billy_j
Author Name: Jit Mark
Author link: https://covid19-data.nist.gov/pid/rest/local/author/jit_mark
Author Name: Yang Juan
Author link: https://covid19-data.nist.gov/pid/rest/local/author/yang_juan
Author Name: Yu Hongjie
Author link: https://covid19-data.nist.gov/pid/rest/local/author/yu_hongjie
Author Name: Edmunds W John
Author link: https://covid19-data.nist.gov/pid/rest/local/author/edmunds_w_john
Author Name: Baguelin Marc
Author link: https://covid19-data.nist.gov/pid/rest/local/author/baguelin_marc
sha: 8d479e31a013c475d0eebb239a1ceae58e86282d
license: cc-by
license_url: https://creativecommons.org/licenses/by/4.0/
source_x: Medline; PMC
source_x_url: https://www.medline.com/https://www.ncbi.nlm.nih.gov/pubmed/
pubmed_id: 35139857
pubmed_id_url: https://www.ncbi.nlm.nih.gov/pubmed/35139857
pmcid: PMC8830135
pmcid_url: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8830135
url: https://www.ncbi.nlm.nih.gov/pubmed/35139857/ https://doi.org/10.1186/s12916-022-02269-5
has_full_text: TRUE
Keywords Extracted from Text Content: High-latitude sub-annual B outpatients inpatients A/H3N2 regional-based low-latitude A/H1N1pdm09 B subtypes High-latitude A/ H3N2 Fig. S19 B inpatients A/H3N2 Fig. S20 all-strain Jiangxi Guizhou postpandemic Tibet Autonomous Region Influenza-like line travellers Fig. S7 B lineages B/Yamagata Fujian Fig. S5 -S8 Tianjin Fig. 3 post-2009/2010 Influenza A/ H1N1pdm09 human A/ H1N1pdm09 subtypes Anhui A/H1N1 extract Fig. S14 contextualises low-latitude parts Fig. 2A B/Victoria lineages low-latitude Shanghai. EIDEC DIA/ Guangxi A/H1N1pdm09 Non-epidemic [11] [12] [13] SARS-CoV-2 outpatients Heilongjiang Fig. S9 Shanghai NIP regional-based Fig. S10 -S13 Fig. S16 -S18 hemisphere people B/Victoria Hongqiao GDP Fig. S15 patients FYS MB EIDEC DIA/ UK participants
Extracted Text Content in Record: First 5000 Characters:Background: China experiences large variations in influenza seasonal activity. We aim to update and improve the current understanding of regional-based within-year variations of influenza activity across mainland China to provide evidence for the planning and optimisation of healthcare strategies. We conducted a systematic review and spatio-temporal meta-analysis to assess regional-based withinyear variations of ILI outpatient consultation rates, influenza test positivity rates amongst both ILI outpatients and SARI inpatients, and influenza-associated excess mortality rates. We searched English and Chinese databases for articles reporting time-series data on the four influenza-related outcomes at the sub-national and sub-annual level. After synthesising the data, we reported on the mean monthly rate, epidemic onset, duration, peak and intensity. We included 247 (7.7%) eligible studies in the analysis. We found within-year influenza patterns to vary across mainland China in relation to latitude and geographic location. High-latitude provinces were characterised by having short and intense annual winter epidemics, whilst most mid-latitude and low-latitude provinces experience semi-annual epidemics or year-round activity. Subtype activity varied across the country, with A/H1N1pdm09 and influenza B occurring predominantly in the winter, whereas A/H3N2 activity exhibited a latitudinal divide with highlatitude regions experiencing a winter peak, whilst mid and low-latitude regions experienced a summer epidemic. Epidemic onsets and peaks also varied, occurring first in the north and later in the southeast. We found positive associations between all influenza health outcomes. In addition, seasonal patterns at the prefecture and county-level broadly resembled their wider province. Conclusions: This is the first systematic review to simultaneously examine the seasonal variation of multiple influenza-related health outcomes at multiple spatial scales across mainland China. The seasonality information provided here has important implications for the planning and optimisation of immunisation programmes and healthcare provision, supporting the need for regional-based approaches to address variations in local epidemiology. Background Each year, seasonal influenza is responsible for a substantial burden of disease [1] [2] [3] . With a total population in excess of 1.4 billion people, mainland China experiences a large influenza morbidity and mortality burden [4] . Each year, it is estimated there are approximately 2.5 influenza-associated influenza-like-illness (ILI) consultations per 1000 people and between 84,200 and 92,000 influenza-associated excess respiratory deaths [5, 6] . Despite this, influenza vaccines are not currently covered by the government-funded National Immunisation Program (NIP) for most of the population in mainland China. Hence, the cost is usually borne by the consumer, resulting in low uptake [7] . In recent years, some wealthier local governments have offered free influenza vaccination to older adults, leading to increased coverage [8] [9] [10] . Influenza seasonality varies substantially both between and within countries [11] . In non-pandemic periods, seasonal influenza epidemics are characterised by strong winter peaks in temperate high and low-latitude regions. Conversely, sub-tropical and tropical regions broadly experience semi-annual influenza peaks or year-round activity [11] [12] [13] . Mainland China spans a vast geographic area and experiences large variations in influenza seasonality. High-latitude provinces have been shown to exhibit influenza seasons similar to those of other temperate regions in the northern hemisphere, whilst mid and low-latitude provinces experience a less pronounced seasonal burden, more reflective of tropical and subtropical regions [14] [15] [16] . Whilst many studies have estimated the burden of influenza-related health outcomes across mainland China, results are often reported at the annual level, neglecting the within-year variations [5, 6] . Meanwhile, studies that examine the within-year seasonal variation of influenza are usually limited to an individual region [17] [18] [19] [20] , or only report on one specific outcome e.g. influenza test positivity rates [14] . Some studies only report on a single influenza season, in a single setting, making it difficult to contextualise both spatially or temporally [21, 22] . Whilst all these studies provide useful elements individually, we aim to synthesise all the available information from both the English and Chinese literature to update and improve the current characterisation of the withinyear seasonal variation of multiple influenza health outcomes across mainland China, at multiple spatial scales. In turn, this will provide evidence for the planning and optimisation of influenza immunisation programmes and public health strategies across mainland China. We collected time-series data on four key influenzarelate
Keywords Extracted from PMC Text: people Fig. S14 contextualises Fig. S7 Fig. S9 Tianjin inpatients line Fig. S20 low-latitude extract Guangxi Heilongjiang Non-epidemic" human High-latitude Fig. S10 - S13 B subtypes B/Yamagata B/Victoria lineages regional-based SARS-CoV-2 Jilin Fig. S15 post-2009/2010 Fig. S19 Fujian " Hongqiao low-latitude parts Guizhou Shanghai 's A/H1N1 B lineages GDP A/H1N1pdm09 Fig. 2A travellers [11–13] hemisphere Fig. S5 - S8 Fig. 3 B/Victoria Jiangxi Anhui A/H3N2 Tibet Autonomous Region Fig. S16 - S18 Shanghai. outpatients B
Extracted PMC Text Content in Record: First 5000 Characters:Each year, seasonal influenza is responsible for a substantial burden of disease [1–3]. With a total population in excess of 1.4 billion people, mainland China experiences a large influenza morbidity and mortality burden [4]. Each year, it is estimated there are approximately 2.5 influenza-associated influenza-like-illness (ILI) consultations per 1000 people and between 84,200 and 92,000 influenza-associated excess respiratory deaths [5, 6]. Despite this, influenza vaccines are not currently covered by the government-funded National Immunisation Program (NIP) for most of the population in mainland China. Hence, the cost is usually borne by the consumer, resulting in low uptake [7]. In recent years, some wealthier local governments have offered free influenza vaccination to older adults, leading to increased coverage [8–10]. Influenza seasonality varies substantially both between and within countries [11]. In non-pandemic periods, seasonal influenza epidemics are characterised by strong winter peaks in temperate high and low-latitude regions. Conversely, sub-tropical and tropical regions broadly experience semi-annual influenza peaks or year-round activity [11–13]. Mainland China spans a vast geographic area and experiences large variations in influenza seasonality. High-latitude provinces have been shown to exhibit influenza seasons similar to those of other temperate regions in the northern hemisphere, whilst mid and low-latitude provinces experience a less pronounced seasonal burden, more reflective of tropical and subtropical regions [14–16]. Whilst many studies have estimated the burden of influenza-related health outcomes across mainland China, results are often reported at the annual level, neglecting the within-year variations [5, 6]. Meanwhile, studies that examine the within-year seasonal variation of influenza are usually limited to an individual region [17–20], or only report on one specific outcome e.g. influenza test positivity rates [14]. Some studies only report on a single influenza season, in a single setting, making it difficult to contextualise both spatially or temporally [21, 22]. Whilst all these studies provide useful elements individually, we aim to synthesise all the available information from both the English and Chinese literature to update and improve the current characterisation of the within-year seasonal variation of multiple influenza health outcomes across mainland China, at multiple spatial scales. In turn, this will provide evidence for the planning and optimisation of influenza immunisation programmes and public health strategies across mainland China. We collected time-series data on four key influenza-related health outcomes across mainland China through a systematic search of both the English and Chinese literature. We selected outcomes to capture all levels of disease severity, this included (1) ILI outpatient consultation rates; (2) influenza test positivity rates amongst both ILI outpatients; (3) severe acute respiratory infection (SARI) inpatients; and (4) influenza-associated excess mortality rates. We further included strain-specific test positivity rates for the most common seasonal influenza strains as a sub-category for the overall test positive rates (i.e. under (2)). This included A/H3N2, A/H1N1pdm09 and influenza B viruses. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [23] and searched four databases (PubMed, Web of Science, WanFang and CNKI) for English or Chinese articles reporting time-series data on any of the above outcomes. The specific search terms included "influenza", "ILI", "test positive", "hospitalisation, "mortality", "China", "time-series" and "seasonality", with many other closely related words and synonyms along with their Chinese translations (Additional file 1: Appendix 1). We limited the literature search to articles released between January 1, 2000, to September 31, 2019, as prior to this there was a lack of consistent laboratory surveillance data widely available across mainland China [14]. Additionally, we aimed to provide a snapshot of the current state of influenza seasonality within China based on recent years; any available historic data prior to this is less likely to be relevant to current seasonality patterns. Each article identified through the search strategy went through a process of title, abstract and full-text screening based upon a set of inclusion and exclusion criteria (Additional file 1: Appendix 2). To ensure consistency between reviewers, we conducted a blind screening on a random sample of 200 articles identified by the search strategy. In this exercise, authors had a high level of agreement between studies (>95%), and any conflicts were discussed and resolved. WebPlotDigitizer (version 4.2 )[24] was used to extract data from figures, the R package tabulizer [25] was used to extract data from tables, and we also collected data from studies where the raw data
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