Burden of medically attended influenza in Norway 2008‐2017

Abstract

Background The burden of influenza in Norway remains uncertain, and data on seasonal variations and differences by age groups are needed. Objective To describe number of patients diagnosed with influenza in Norway each season and the number treated in primary or specialist health care by age. Further, to compare the burden of seasonal influenza with the 2009‐2010 pandemic outbreak. Methods We used Norwegian national health registries and identified all patients diagnosed with influenza from 2008 to 2017. We calculated seasonal rates, compared hospitalized patients with patients in primary care and compared seasonal influenza with the 2009‐2010 pandemic outbreak. Results Each season, on average 1.7% of the population were diagnosed with influenza in primary care, the average rate of hospitalization was 48 per 100 000 population while the average number of hospitalized patients each season was nearly 2500. The number of hospitalized influenza patients ranged from 579 in 2008‐2009 to 4973 in 2016‐2017. Rates in primary care were highest among young adults while hospitalization rates were highest in patients 80 years and older and in children below 5 years. The majority of in‐hospital deaths were in patients 70 years and older. Fewer patients were hospitalized during the 2009‐2010 pandemic than in seasonal outbreaks, but during the pandemic, more people in the younger age groups were hospitalized and fatal cases were younger. Conclusion Influenza causes a substantial burden in primary care and hospitals. In non‐pandemic seasons, people above 80 years have the highest risk of influenza hospitalization and death.

Characteristics of hospitalizations with an influenza diagnosis, France, 2012‐2013 to 2016‐2017 influenza seasons

“…Previous studies highlighted the high impact of the very elderly on mobilization of hospital resources for example in England in age-group ≥75 years 13 or in Norway in age-group ≥80 years. 9 In our report, a marked shift in influenza hospital burden was found in ≥80 years. Indeed, being aged 80 years and older was the paramount factor associated with the highest hospitalization rate, proportion of death, number of hospitalization days, the longest length of stay, and the highest proportion of a severe influenza diagnosis-related group (DRG) during the study period.…”

“…Hospital discharge databases are a valuable source of information to estimate the burden of hospitalized seasonal influenza cases. [3][4][5][6][7][8][9] In France, a recent evaluation of the completeness of the ICU surveillance system for influenza cases, using capture-recapture methods, estimated the exhaustivity of the French national hospital discharge database (PMSI) to 73%. 10 Using the PMSI database in order to estimate the burden of severe influenza illness in hospital is consequently of relevance.…”

“…However, in that particular season, the burden in the elderly was low, in line with previous findings. 9,16 This observation was attributed to repeated exposures to the virus over a 40-…”

Estimation of influenza‐ and respiratory syncytial virus‐attributable medically attended acute respiratory infections in Germany, 2010/11‐2017/18

“…For example, a recent review of the literature on the burden of influenza B noted that although the “findings suggest that influenza B can pose a significant burden to the global population,” “there are serious gaps in the understanding of the precise magnitude.” The review did not even attempt to address each influenza B lineage separately. Other recently published estimates did not recognize the specific role of influenza subtypes and lineages …”

“…Other recently published estimates did not recognize the specific role of influenza subtypes and lineages. 5,6 Another major player in the family of respiratory viruses with substantial impact in the winter season is the respiratory syncytial virus (RSV). Both viruses cause a similar syndrome (influenza-like illness, ILI), but influenza as well as RSV may also present without fever.…”