Global mortality associated with seasonal influenza epidemics: New burden estimates and predictors from the GLaMOR Project

Abstract

BackgroundUntil recently, the World Health Organization (WHO) estimated the annual mortality burden of influenza to be 250 000 to 500 000 all-cause deaths globally; however, a 2017 study indicated a substantially higher mortality burden, at 290 000-650 000 influenza-associated deaths from respiratory causes alone, and a 2019 study estimated 99 000-200 000 deaths from lower respiratory tract infections directly caused by influenza. Here we revisit global and regional estimates of influenza mortality burden and explore mortality trends over time and geography.MethodsWe compiled influenza-associated excess respiratory mortality estimates for 31 countries representing 5 WHO regions during 2002-2011. From these we extrapolated the influenza burden for all 193 countries of the world using a multiple imputation approach. We then used mixed linear regression models to identify factors associated with high seasonal influenza mortality burden, including influenza types and subtypes, health care and socio-demographic development indicators, and baseline mortality levels.ResultsWe estimated an average of 389 000 (uncertainty range 294 000-518 000) respiratory deaths were associated with influenza globally each year during the study period, corresponding to ~ 2% of all annual respiratory deaths. Of these, 67% were among people 65 years and older. Global burden estimates were robust to the choice of countries included in the extrapolation model. For people <65 years, higher baseline respiratory mortality, lower level of access to health care and seasons dominated by the A(H1N1)pdm09 subtype were associated with higher influenza-associated mortality, while lower level of socio-demographic development and A(H3N2) dominance was associated with higher influenza mortality in adults ≥65 years.ConclusionsOur global estimate of influenza-associated excess respiratory mortality is consistent with the 2017 estimate, despite a different modelling strategy, and the lower 2019 estimate which only captured deaths directly caused by influenza. Our finding that baseline respiratory mortality and access to health care are associated with influenza-related mortality in persons <65 years suggests that health care improvements in low and middle-income countries might substantially reduce seasonal influenza mortality. Our estimates add to the body of evidence on the variation in influenza burden over time and geography, and begin to address the relationship between influenza-associated mortality, health and development.

Robust Estimation of Infection Fatality Rates during the Early Phase of a Pandemic

“…To control for this distortion by selection bias aiming at enriching for positive cases in the test pool Nt we need to adjust the overestimated prevalence p with the unknown factor f to turn the CFR′ −0 into the IFR −0 . In (1) the calculated CFR is determined rather too high and does not represent an IFR, because of just the same distortion factor f as in (3). Since testers selectively address the pool of diseased persons, into the pool of persons tested Nt, they will therefore also increase the risk of death that would be representative for the population of all infected persons, which should be reflected by our IFR.…”

“…Likewise, we will need to correct CFRn-0 by the same factor f as in (3). In this case, IFR −0 can be calculated as:…”

“…This pandemic contributed to the premature death of 1 percent of the world population at the time being 2 . On the other hand, despite all non-refutable morbidity, COVID-19 may fall short of provoking a comparable impact on mortality as the seasonal Influenza, which is estimated to contribute to 389,000 deaths per year on average 3 . Experts conclude that there is still a range for CFR of 0.1 up to 1.0, which practically spoken is reflecting the margin from normal seasonal Influenza to the lower boundary CFR estimate of 1918-1919 H1N1 Influenza 4 .…”

Epidemic prevention and control measures in China significantly curbed the epidemic of COVID-19 and influenza

“…Overall the mortality associated with influenza in China for adults aged 60 years or older were 38.5 per 100,000 person-seasonal, and for individuals younger under 60 years was 1.5 per 100,000 person-seasonal through 2010 to 2015 12 . According to the research of John Paget, overall rate of influenza-associated excess respiratory deaths for adults aged 65 years or older was 53.7 per 100,000 person-seasonal, while the mortality for individuals younger was 2.1 per 100,000 person-seasonal through 2002 to 2012 13 . The annual health economic burden associated with influenza should not be ignored [13][14][15] .…”

‘More dangerous than terrorism’ – the media verus the facts

“…And finally, just something to think about: a recent study suggests that the global mortality from seasonal influenza is estimated to be around 294 000 to 500 000 deaths annually. [5] While nothing like the potential number of deaths should this coronavirus end up infecting 60% of the world's population, this is not an insignificant number of deaths from a disease that we more or less ignore each year. There are a few lessons to be learnt from the media response to this outbreak, I think.…”