Posted on 06 January 2023

RSV, Covid, Strep, Flu… there are many abbreviations floating about this winter in the UK, and many of them describe a litany of illnesses plaguing the nation. It’s the annual flu season, yet there are many accomplices along the way – amidst a backdrop of the worst A&E wait times on record, causing panic and fear that patients themselves may not get treated in adequate time. Some are describing this flu season as the worst ever – is it down to the pathogenicity of virus, or the extenuating factors surrounding infection which are hitting doubly hard in this period of intense healthcare pressure?

Belgium announced just yesterday (5th January) a major flu epidemic with other European nations also feeling the squeeze from a new variant (which is no surprise, flu mutates every year). Last year in the UK, 82% of people aged 65 and over came forward for their influenza vaccination, an increase from the previous period due, in part, to an aggressive NHS campaign to increase awareness. As the 22/23 flu season is in full swing, we do not have those numbers, yet in adults under 65 in a clinical risk group this number for the previous season was as low as 50%. This should not be taken likely, bearing in mind the at- risk group includes people with breathing issues, cancers, immune problems, and other long-term conditions and serious cardiovascular disorders.

NHS England released a press briefing last week showing the impact influenza was having on the service. Discussing the cases and severity, a spokesperson said, ‘New data out today shows there were 3,746 patients a day in hospital with flu last week, up from 520 a month ago (w/e 27 Nov). Of those in hospital last week, 267 were in critical care beds. As viruses re-circulate after a hiatus during the pandemic the NHS has continued to see hospital cases grow week on week, up almost 80% in seven days (from 2,088 w/e 18 Dec)’. Rather frighteningly, the report goes on to say that in last year’s flu season by the exact week, only 34 patients were in hospital for flu and only 2 in critical care. Now, there is a discussion here around the virulency of the Omicron variant at that time in England and the competitive edge that had in being pathogenic and infectious to individuals, with a much larger percentage of hospital and doctor calls at that time being for coronavirus. Ironically, the fact coronavirus was the dominant pathogen at that time is precisely why we are struggling badly now with influenza – our immune systems (without vaccination) haven’t ‘seen’ the influenza pathogen in years.

Writing in Nature, Cassandra Willyard discusses the term ‘Immunity Debt’ which describes our naivety to pathogens that we haven’t seen, because most times we’ve found ourselves ill from respiratory symptoms in the last two years we’ve thought, “oh no… covid”. ‘In August 2021, researchers in France coined the term ‘immunity debt’ to describe this reduction in population-level immunity. On Twitter, the term has taken on a life of its own. Some people have taken it to mean that a lack of exposure to pathogens such as RSV and influenza has irrevocably damaged the immune system’ she writes. Now, there’s no need for panic at an interpretation that the lack of exposure has damaged the immune system, but it is true we are certainly more ‘naïve’ as a population to these other pathogens.

With coronavirus being the most dominant respiratory pathogen in recent years, it’s ancestral mutation towards higher infectivity, lower virulence has meant that more people are exposed to the pathogen, leading way for niches for other respiratory viruses. Where people may be naïve to flu, the term describes that the immune system lacks on demand antibodies in the blood to neutralise the flu virus, and the ancestral long term pathogen protection in specialist antibodies may be out of date due to the gap in years since the last neutralisation. This, in tandem with a higher pathogenicity of the flu, means that when people are getting infected – they’re tending to have particularly severe symptoms if they’re unvaccinated, a similar phenomenon with coronavirus which explains the emergency services pressures. The best advice, if you are eligible, keep up to date with your flu vaccination.

Share this article