A new study from ECDC investigators highlights mortality and risk factors associated with seasonal influenza.
Diseases like Zika and Ebola still get all the headlines.
However, those in the know, well, know that another, far-more-common bug—influenza—is the one that truly sickens and kills on a global scale. Now, as 2019-20 flu seasons begins to ramp up, an analysis by investigators at the European Centre for Disease Prevention and Control (ECDC) highlights just how deadly the virus can be. The findings were published on October 29th in Open Forum Infectious Diseases.
“We are well aware that influenza infection can cause severe disease and mortality as we observe this in different magnitudes season by season,” co-author Cornelia Adlhoch, DVM, PhD, expert in respiratory diseases and influenza, ECDC, told Contagion®.
Adlhoch and her colleagues analyzing influenza data from hospitals’ intensive care units within European Union (EU) over an 9-year period, from 2009 through 2017, using descriptive analysis and Poisson regression models with “robust variance” to estimate any association between age, sex, virus subtype, and comorbidities with fatal outcome following confirmed diagnosis.
Of the 13,368 influenza cases included in the basic dataset, 2806 (21%) were fatal, a remarkable number when you consider how (relatively) little coverage flu-related mortality receives in the mainstream media, both here and abroad. Adlhoch and her team also found that influenza virus A(H1N1)pdm09 or A(H3N2) infection, age ≥60 years, and prior diagnosis of cancer, HIV infection and/or other immune deficiency and heart, kidney, and liver disease increased risk for death linked with virus. Notably, however, risk of death was lower for patients with chronic lung disease and for pregnant women.
“We do see that the circulation of the A(H3N2) virus type mostly affects the elderly with increased excess mortality in this age group in the general population, while A(H1N1)pdm09 virus affects more the middle-aged people,” Adlhoch added. “However, we need to be careful to not over-interpret our surveillance data from intensive care units as not all countries collect and report outcome data comprehensively from all patients in every hospital. We, therefore, cannot calculate in-hospital mortality rates per se. It might also be the case that more detailed information is collected from very severe and fatal cases.”
Still, though, the ECDC authors acknowledge that their main goal in performing this analysis was to “raise awareness that people of older age, or those who suffer from underlying conditions like cancer, HIV/immune suppression or other chronic diseases, are at particular risk of a fatal outcome” from influenza—a warning cry we can’t help but associate with former Fox News host Shepard Smith, who famously put the Ebola “crisis” in the United States in 2014 into perspective on live television. It is hoped that the general public will respond by getting vaccinated against influenza, and that their physicians will encourage them to do so, they added.
“Vaccination against influenza is one important measure to prevent severe disease and associated mortality together with early antiviral treatment,” Adlhoch noted. “Although the information on individual vaccination within our dataset is limited, we observed a protective effect. This is in line with recent evidence that seasonal vaccination decreases severe outcomes despite variable and waning vaccine effectiveness, lower immune response in the elderly as well as the patients’ underlying co-morbidities and clinical complications during the course of disease.”