The season of festive flu testing looms large
Every winter brings a baseline level of influenza, and this year Ireland is again bracing for a testing season filled with flu and cold outbreaks.
This winter’s flu arrived a bit earlier than usual and is predominantly driven by a mutated A(H3N2) strain. Early starts in flu seasons are often linked to greater severity.
In recent years, A(H1N1) has tended to be the more dominant strain, while A(H3N2) was the main driver in earlier seasons. Because many people have limited recent exposure to this particular variant, immunity levels against it are relatively low.
The H3N2 flu strain tends to be particularly aggressive, bearing similarities to the lineage responsible for the 1968 Hong Kong flu epidemic.
Professor Ronan Collins, a Consultant Geriatrician at Tallaght University Hospital, emphasizes that influenza isn’t merely a respiratory illness. It can have serious impacts on the heart and is a significant risk factor for stroke.
He also notes that in some individuals influenza can trigger delirium or brain confusion—a toxic state that can hasten the onset of dementia in certain cases.
Notably, up to 75% of people with influenza may show no symptoms, yet they can still spread the infection.
Health authorities reported 2,944 confirmed influenza cases in the week ending last Saturday, with 657 people hospitalized with the illness.
Government data indicate that well over three-quarters of those currently in hospital with influenza are not vaccinated.
Dr Conor Deasy, President of the Irish Association of Emergency Medicine, described this season’s strain as particularly nasty and said the surge is stressing hospitals that are already crowded.
Symptoms
Influenza-like illness is marked by a sudden onset of fever of 38°C or higher, in the absence of another cause, plus at least two of the following: dry cough, headache, muscle aches, and sore throat.
Last season saw a substantial outbreak, with 21,297 reported cases, compared with 11,751 in 2023 and 10,392 in 2022.
During the pandemic year of 2021, when lockdowns and restrictions were in place, only 39 flu cases were reported.
In 2020, the first year of the pandemic, 7,775 flu cases were recorded.
Flu deaths
So far this season, 13 people have died from influenza.
Influenza was classified as a notifiable disease in Ireland in January 2004.
In typical flu seasons, 200-500 deaths are reported, though very severe seasons can see much higher tolls.
HPSC analyses suggest there can be between 400 and 800 excess deaths attributable to influenza, with particularly harsh seasons yielding 1,000 to 1,200 excess deaths.
Hospitals and elderly people
The HSE notes that influenza tends to be more severe among older adults, those with chronic heart or lung disease, children under four, people with cerebral palsy, and pregnant women.
Most influenza fatalities—about 80–90%—occur in the elderly, often due to secondary bacterial pneumonia or worsening of pre-existing conditions such as COPD or heart disease.
The surge in flu cases also compounds pressures on emergency departments and can lead to more overcrowding.
RSV and Covid-19
While RSV and Covid-19 circulate, their levels are considerably lower than influenza this season. For the week ending last Saturday, there were 368 RSV-confirmed cases and 176 confirmed Covid-19 cases.
Since the season began, 7,506 influenza cases have been confirmed, with the highest numbers concentrated in Dublin, Cork, Westmeath, Galway, and Wexford. Laois, Mayo, and Monaghan reported the fewest cases.
Northern Hemisphere seasonality
According to HPSC, influenza activity in the Northern Hemisphere typically begins in October and runs through May.
This surge is not unique to Ireland; England is experiencing record-high numbers for this time of year, with the NHS warning of a worst-case scenario. Northern Ireland is also seeing rising cases.
Outbreak dynamics and affected groups
Flu outbreaks generally last six to eight weeks and can affect all ages, with the very young and very old being most vulnerable.
In the week prior to last Saturday, there were 28 hospital outbreaks and 23 in nursing homes.
Nursing Homes Ireland notes there is no immediate cause for alarm regarding preparation, and given the importance of social interaction in nursing home life, restrictions would only be used if absolutely necessary.
More than 80% of nursing home residents have received the vaccine, which will help reduce spread and severity.
Vaccination and public health messaging
Experts stress that the best defense for any flu season is vaccination, ideally before it begins. However, late December and early January still present a window where vaccination can be beneficial, since the vaccine typically takes about two weeks to become protective.
The HSE offers flu vaccines free of charge through GPs, pharmacies, and in nursing homes for many age groups.
Vaccination uptake among health-care workers is a persistent issue. The HSE’s target is 75%, but this level has not been achieved consistently, which can send mixed signals to the public about the seriousness of the threat.
Past years have shown wide variation in staff vaccination rates—from as low as 18% (2011–2012) to over 71% (2020–2021). For the 2024/25 season, health-care worker uptake stood at 45%.
Protecting healthcare workers protects patients too, and reducing staff illness helps keep hospitals staffed during a very busy period.
Calls for enhanced vaccines
Recent reporting highlighted that the HSE did not offer the enhanced adjuvanted vaccine for those aged 65 and older, deeming it not cost-effective. The standard vaccine was provided instead.
HIQA had suggested that using an adjuvanted vaccine for seniors could be a better use of resources, depending on cost, and several countries already provide enhanced vaccines to some or all seniors.
This raises the question: to what extent could the current and anticipated pressures on hospitals, GPs, and patients have been eased if the enhanced vaccine had been available this season?
Clinical perspectives
Dr Colm Henry, the HSE’s Chief Clinical Officer, said the vaccine available this season is highly effective and that all licensed vaccines comply with WHO recommendations for the season.
A British Medical Journal report this week warned that existing vaccines might not be as effective against the current strain as hoped. That concern can fuel doubts about vaccination, but doctors urge people to get the latest vaccine, since it generally performs as expected.
UK data show the current vaccines are about 70–75% effective at preventing hospitalizations in children aged 2–17 and 30–40% effective in adults.
Planned operations and holiday season
Traditionally, hospitals reduce elective surgeries around Christmas and New Year to allow staff downtime and to avoid hospital stays during the holiday season. With influenza peaking during Christmas week, more planned procedures may be postponed than usual, and visiting restrictions could be reintroduced to curb outbreak spread, as was common during the Covid-19 era.
All signs point to a challenging season ahead for patients, health workers, and the health system overall.
