ECDC Warns Of Potentially Severe Flu Season Ahead

 Disease Burden of Flu - Credit CDC

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Although exact numbers are impossible to calculate, the CDC estimates in an average year, between 12,000 and 52,000 Americans die from influenza.  Since influenza can trigger other (often fatal) disease processes (see JAHA: Study Linking ILI To Increased Risk Of Heart Attack & Stroke), and the cause of death - particularly in the elderly - is never fully explored, those numbers could well be higher. 

Flu seasons vary widely, as the CDC chart above illustrates. Last year (not shown), with COVID dominating and NPIs (social distancing, face masks, etc.) in wide use, flu was virtually a no show. 

But the 2011-2012 flu season was well below average (est. 12,000 deaths) while deaths in 2014-2015, and 2017-2018 were estimated more than 4 times higher (est 51,000-52,000) (see the CDC's Disease Burden of Flu).

The `unofficial' benchmark for a flu pandemic has often been pegged at 100,000 U.S. deaths in a season. All of which makes 736,000 American deaths from COVID since the spring of 2020 a clear indicator of its impact. 

This year, with many of the COVID restrictions from last year no longer in effect - and community immunity to influenza likely low -  many public health agencies are expecting a return of influenza, and a possible `twindemic' of influenza and COVID (see UK: Preparing For A "Reasonable Worst-Case" Winter Scenario).

Not only would flu cases add to the burden of hospitals trying to cope with the demands of COVID, there are a few studies which suggest COVID-Influenza coinfection could be deadlier than having  either infection on its own. 

Nature: Increased Lethality in Influenza & SARS-CoV-2 Coinfection is Prevented by Influenza Immunity but not SARS-CoV-2 Immunity (in mice)

Cureus: A Case Series of SARS-CoV-2 and Influenza Co-infection

PHE Study: Co-Infection With COVID-19 & Seasonal Influenza

Any way you slice it, when influenza does return, it is likely to slam us pretty hard.  Maybe that happens this winter, maybe not until next fall.  No one can accurately predict what flu will do.  But if it returns while COVID is still rife, hospitals could be severely tested. 

While reports of influenza remain limited around the world, in recent weeks we've begun to see reports of increased flu activity in Eastern Europe, Russia, and parts of Asia. Two days ago the WHO reported:

National Influenza Centres (NICs) and other national influenza laboratories from 95 countries, areas or territories reported data to FluNet for the time period from 27 September 2021 to 10 October 2021 (data as of 2021-10-22 07:48:51 UTC). The WHO GISRS laboratories tested more than 240 512 specimens during that time period. 2219 were positive for influenza viruses, of which 763 (34.4%) were typed as influenza A and 1456 (65.6%) as influenza B.

Of the sub-typed influenza A viruses, 169 (34%) were influenza A(H1N1)pdm09 and 328 (66%) were influenza A(H3N2). Of the characterized B viruses, 2 (0.1%) belonged to the B-Yamagata lineage and 1339 (99.9%) to the B-Victoria lineage.

While influenza A is viewed as the bigger epidemic threat, influenza B is no slouch (see ERJ: When “B” becomes “A” : The Emerging Threat of Influenza B Virus). And of the two influenza A subtypes currently circulating, A/H3N2 generally produces the most severe flu season, particularly among the elderly.

All reasons why - even though flu activity remains reassuringly low - the ECDC issued the following warning yesterday. 

Early influenza cases indicate the possibility of severe upcoming season for elderly

Press release
26 Oct 2021
 
Although the overall number of influenza detections in the majority of EU/EEA countries is still low, indications show that influenza circulation is above the seasonal threshold in Croatia, which is unusually early. The main reported subtype among the cases recorded in EU/EEA during the past month is A(H3N2), which disproportionally affects older people, and is associated with lower vaccine effectiveness. This is a sign that the upcoming influenza season could be severe for elderly people, and that influenza patterns may vary between countries in terms of timing.

“The early detections of the A (H3N2) subtype are an indication that the upcoming flu season could be severe, although we cannot know for sure what the upcoming flu season will look like,” said Pasi Penttinen, Head of ECDC’s influenza programme. “A steep rise in flu infections during the ongoing COVID-19 pandemic could have serious consequences for the elderly and those with weak immune systems and could place an additional burden on health systems already strained by COVID-19. It is therefore important that we take the necessary precautions and protect those that are most at risk,” said Pasi Penttinen.

During the 2020-2021 season, there was a remarkable decrease (>99%) in the number of influenza infections detected in the EU/EEA, with numbers detected being similar to those reported during inter-seasonal periods. This indicates that non-pharmaceutical interventions, such as avoiding unnecessary crowding and the maintenance of hygiene measures are effective in not only curbing the spread of SARS-CoV-2 but also influenza.

“From our experience with the COVID-19 pandemic, we have further evidence that non-pharmaceutical interventions such as physical distancing and hygiene measures can effectively curb the spread of influenza. This is especially important to consider in environments such as nursing homes and healthcare settings” said Pasi Penttinen.

“Vaccination against SARS-CoV-2 and flu also provides good protection against severe disease. Those working in a healthcare setting or a nursing home should ensure that they are vaccinated against both SARS-CoV-2 and flu before the winter months.”

Approximately 20% of the population become infected with influenza each year and one in four infected people will develop symptoms. The elderly, pregnant women and those with chronic medical conditions like heart disease, problems with the lungs and airways, diabetes or immune system problems are most at risk of experiencing severe complications by influenza.

Antiviral medicines, taken as rapidly as possible after the onset of symptoms, are safe and effective measures for the treatment of flu and are generally recommended for severe or rapidly progressing cases. Their prophylactic properties are also useful as a preventive measure during events such as nursing home outbreaks.

While no one can say just how close of a match, or how effective, this year's flu vaccine will be until the end of the flu season, I've already gotten mine (see #NatlPrep: Giving Your Preparedness Plan A Shot In The Arm), and I'll be grateful for whatever protection it does provide.

I'll also continue to mask up when in public, avoid crowds where I can, and practice good hand hygiene.  Not only for my own personal wellbeing, but to keep from adding to the burden on local healthcare delivery systems. 

In The Realities Of Crisis Standards Of Care, we looked at how overburdened hospitals could affect anyone seeking medical care this fall and winter, potentially making this a very bad time to have a heart attack, stroke, or get in a car wreck.

While getting the flu and COVID vaccines (and boosters), and faithfully using NPIs, can't guarantee you'll come away unscathed from this winter's respiratory season - combined, they can greatly lower your odds of becoming a statistic. 

And given the uncertainties of the months ahead, it is worth seeking whatever advantages you can get.