Influenza-associated mortality

Influenza-associated mortality refers to deaths attributed to seasonal influenza infection at the population level ^[1]. Estimates have been reported as influenza-associated all-cause mortality rates per 100,000 persons ^[1].

Influenza-associated mortality predominantly affects older adults aged 65 years and above, young children under 5 years, and individuals with chronic diseases ^[1][2]. Children under 5 years experience the highest rates of influenza-associated hospitalizations and outpatient visits for influenza-like illness, indicating severe clinical presentations in this age group ^[1]. The mortality burden shows a bimodal distribution with peak vulnerability at both extremes of age ^[1].

Seasonal influenza-associated mortality imposes a substantial population burden ^[1]. In mainland China, pooled influenza-associated all-cause mortality rates were 14.33 per 100,000 persons for all ages and 122.79 per 100,000 persons for people aged ≥65 years ^[1]. People aged ≥65 years and children younger than 5 years contribute mostly to influenza mortality and morbidity burden ^[1]. A mainland China mortality-burden review reported higher influenza-associated mortality burden in elderly populations, with all-cause excess mortality rates ranging from 49.57 to 228.16 per 100,000 persons ^[3]. Estimates vary substantially by age group, cause-of-death definition, statistical model, geographic location, and study period ^[1].

Older adults, especially people aged ≥65 years, are at high risk of influenza-associated mortality, with pooled rates of 122.79 per 100,000 persons ^[1]. Children younger than 5 years also contribute substantially to influenza mortality and morbidity burden ^[1]. These age groups together account for most of the mortality and morbidity burden due to influenza ^[1].

Influenza-associated mortality estimates should be interpreted as population-based, pooled estimates of deaths attributed to seasonal influenza infection ^[1]. Cross-study comparisons should account for heterogeneity by age group, cause-of-death definition, statistical model, geographic location, and study period ^[1]. Publication-bias assessment found no significant bias in pooled all-cause mortality estimates, but heterogeneity remains substantial ^[1].

1. 1Li J et al. Influenza-associated disease burden in mainland China: a systematic review and meta-analysis. Sci Rep. 2021 Feb 3. PMID: 33536462. doi: 10.1038/s41598-021-82161-z.PubMed: https://pubmed.ncbi.nlm.nih.gov/33536462/
2. 2Chua SCJH et al. A Review and Meta-Analysis of Influenza Interactome Studies. Front Microbiol. 2022. PMID: 35531276. doi: 10.3389/fmicb.2022.869406.PubMed: https://pubmed.ncbi.nlm.nih.gov/35531276/
3. 3Li S et al. [The mortality burden of influenza in China: a systematic review]. Zhonghua Yu Fang Yi Xue Za Zhi. 2019 Oct 6. PMID: 31607054. doi: 10.3760/cma.j.issn.0253-9624.2019.10.018.PubMed: https://pubmed.ncbi.nlm.nih.gov/31607054/