2025 Flu Season in Europe: Influenza A takes the lead
The 2025 flu season has started earlier in several European countries and is showing higher-than-usual activity. Organisations such as the World Health Organization (WHO) and the European Centre for Disease Prevention and Control (ECDC) have warned about an early rise in respiratory virus circulation across the region, with Influenza A clearly predominating.
A significant increase is also being seen in Spain. In Catalonia, for example, surveillance data show a very rapid rise in incidence and a demanding healthcare situation as the holiday season approaches.
In this context, detecting influenza is no longer always enough. Identifying which Influenza A subtype is circulating, such as A(H3N2) or A(H1N1)pdm09), provides valuable information for epidemiological surveillance and supports public health decision-making during seasonal peaks.
What is influenza (flu), and why does it change every year?
Influenza, commonly known as flu, is an infectious disease caused by RNA viruses that mainly affects the respiratory tract. Influenza viruses are classified into types A, B and C and are known for their high genetic variability, which helps explain why each season can look and behave differently.
With Influenza A, new subtypes can also emerge through genetic exchange between human and animal strains. This is why terms such as H1N1, H3N2 or H5N1 are epidemiologically relevant—and why subtyping becomes important once Influenza A is detected.
Influenza A symptoms and risk groups
Influenza A typically presents with respiratory and systemic symptoms that can vary in severity depending on a patient’s age and overall health. The most common symptoms include sudden-onset high fever, dry cough, muscle and joint pain, headache, sore throat, marked fatigue and general malaise.
While most cases resolve without complications, Influenza A can cause severe illness in certain risk groups, including young children, older adults, pregnant women and people with chronic conditions or weakened immune systems. For these patients, fast and accurate laboratory diagnosis is especially important to support clinical management and epidemiological surveillance during seasonal peaks.
Flu epidemic 2025 in Spain and Europe: what we’re seeing
During the winter of 2025, influenza activity has increased earlier than usual across Europe. The WHO Regional Office for Europe has confirmed that the influenza season is already underway and has emphasized the importance of strengthening surveillance and vaccination.
The ECDC, through its ERVISS dashboard (European Respiratory Virus Surveillance Summary), provides weekly monitoring of influenza, RSV and SARS-CoV-2 across the EU/EEA and the WHO European Region. This integrated surveillance helps track which viruses are circulating and how intense activity is.
In Spain, multiple reports have highlighted an early increase in cases and the resulting pressure on healthcare services, with particular attention to the predominance of Influenza A.
Why laboratory diagnosis is critical during an Influenza A epidemic
As respiratory virus circulation rises, symptoms can easily overlap between influenza, RSV and COVID-19. During peak season, relying only on clinical presentation can create diagnostic uncertainty, especially in vulnerable patients or high-demand care settings.
In this scenario, laboratory testing provides clear value by enabling:
- Rapid differential diagnosis when multiple viruses are co-circulating
- Reliable confirmation during periods of high clinical demand
- Data that support epidemiological surveillance when Influenza A predominates
PCR for influenza: a molecular strategy aligned with WHO and ECDC guidance
International recommendations for influenza testing during respiratory season generally follow a stepwise approach: start with molecular screening that covers the most relevant respiratory viruses and, when Influenza A is detected, move to confirmation and subtype characterization to provide additional epidemiological insight.
This approach is particularly useful when the season starts early and pressure on healthcare systems increases, as has been observed across Europe in 2025.
Vircell solutions for molecular diagnosis of Influenza A and B
Multiplex screening of respiratory viruses (first-line)
SARS-CoV-2 / FLU A / FLU B / RSV REALTIME PCR KIT (RTPCR021)
A multiplex RT-PCR assay that enables the simultaneous detection of Influenza A, Influenza B, RSV and SARS-CoV-2 in respiratory samples, helping laboratories prioritize and streamline differential diagnosis during periods of high viral circulation.
Key benefits of this approach include:
- Coverage of the most prevalent respiratory viruses during the season
- Support for efficient workflows as sample volumes increase
- A robust basis for identifying Influenza A–positive samples that may require subsequent subtyping
Influenza A subtyping (confirmation and surveillance)
FLU A SUBTYPING REALTIME PCR KIT (RTPCR037-LP-R · RUO)
When Influenza A is detected, knowing the subtype can provide an additional layer of insight—especially in seasons dominated by subtypes such as A(H3N2) or A(H1N1)pdm09).
This kit is designed to detect and differentiate key subtypes, including:
- A(H1N1)pdm09
- A(H3N2)
- A(H5)
Including H5 is particularly relevant in the current context, as highly pathogenic avian influenza continues to be reported in wild birds in parts of Europe and sporadic human cases have also been described internationally, typically linked to exposure to infected animals or contaminated environments. This is why robust subtyping tools matter: they strengthen surveillance and, when avian subtypes such as H5 are detected, they support the next steps recommended for further characterization.
Frequently asked questions about Influenza A
What is Influenza A?
Influenza A is a type of influenza virus with a high mutation rate and seasonal circulation, responsible for most flu epidemics.
Which Influenza A subtypes are circulating in 2025?
During the 2025 flu season, A(H3N2) and A(H1N1)pdm09) are among the predominant subtypes detected in Europe.
Why is Influenza A subtyping important?
Subtyping helps determine which variants are circulating, supporting epidemiological surveillance and public health response.
How is Influenza A diagnosed in the laboratory?
Real-time PCR is the reference method, allowing laboratories to detect and differentiate Influenza A from other respiratory viruses.
🔗 Learn more about influenza and Vircell’s solutions for Influenza A and Influenza B diagnosis.