Europe's Flu Season Starts Four Weeks Early Due to New Variant

Early Onset of Influenza Season Raises Concerns Across Europe

The annual influenza season in Europe has begun approximately four weeks earlier than usual, according to the World Health Organization (WHO). This unusually early start is being driven by a new influenza variant that has rapidly spread across the continent, putting significant pressure on healthcare systems already strained by multiple respiratory viruses circulating simultaneously.

WHO Regional Director for Europe, Dr. Hans Kluge, stated: 'This shows that even a small change in the virus can cause enormous pressure on the health system. That's because people have not built up immunity against it.' The new variant, identified as influenza A(H3N2) subclade K (J.2.4.1), has been detected in at least 27 of the 38 countries in the WHO European Region and accounts for approximately 90% of current influenza cases.

The New Variant: What We Know

The J.2.4.1 subclade represents a significant genetic shift from previous influenza strains, with seven new mutations differentiating it from the vaccine strain selected for the 2025-2026 season. First detected in Australia and New Zealand in August 2025, the variant has since spread to over 30 countries globally. Despite its rapid transmission, WHO officials emphasize there is no evidence that this variant causes more severe illness than previous strains.

According to WHO reports, early data shows that existing influenza vaccines still offer meaningful protection, with approximately 75% effectiveness against severe disease and hospitalization in children aged 2-17, and 35% effectiveness in adults. 'Vaccination remains the most effective defense, especially for high-risk populations,' noted a WHO spokesperson.

Healthcare Systems Under Pressure

The early and intense influenza season comes at a particularly challenging time for European healthcare systems. Many countries are simultaneously dealing with COVID-19, Respiratory Syncytial Virus (RSV), and other respiratory pathogens. In the United Kingdom, the situation has reached critical levels, with NHS officials describing it as a 'worst-case scenario' December.

UK Health Minister Wes Streeting recently called on healthcare unions not to proceed with planned strikes, citing unprecedented pressure on hospitals. 'The pressure on hospitals is the highest since the COVID-19 pandemic,' Streeting stated. Data from England shows that an average of 2,660 patients per day were hospitalized with influenza last week—a 55% increase from the previous week and the highest ever recorded for this time of year.

According to NHS reports, 95% of hospital beds were occupied at the beginning of December, with increasing numbers of healthcare staff also falling ill, further straining the system's capacity.

The Situation in the Netherlands

In the Netherlands, the National Institute for Public Health and the Environment (RIVM) and the Netherlands Institute for Health Services Research (Nivel) are closely monitoring influenza activity. Last week, the country recorded 40 patients per 100,000 inhabitants with influenza-like symptoms, primarily affecting the youngest age group (0-14 years). This represents a significant increase from the 25 patients per 100,000 recorded during the same period last year.

The Netherlands officially declares an influenza epidemic when at least 53 out of 100,000 people report influenza-like symptoms to their general practitioner for two consecutive weeks. While the country has not yet reached this threshold nationally, regional variations show increasing pressure on healthcare services.

Vaccination Effectiveness and Recommendations

Despite the genetic mismatch between the circulating strain and the current vaccine composition, health authorities across Europe continue to emphasize the importance of vaccination. Early data from the United Kingdom shows that vaccination still prevents patients from becoming seriously ill, even with the new variant.

A European study published in Eurosurveillance shows interim vaccine effectiveness estimates ranging from 32-53% in primary care settings and 33-56% in hospital settings for influenza A viruses. The research, conducted by the European Influenza Vaccine Effectiveness (IVE) group across 17 countries, indicates higher effectiveness against influenza B viruses (≥58% across settings).

WHO recommends several protective measures beyond vaccination: staying home when sick, practicing good hand and respiratory hygiene, improving ventilation in indoor spaces, and wearing masks when symptomatic. These measures are particularly important as the holiday season approaches, when increased social gatherings typically lead to higher transmission of respiratory viruses.

Looking Ahead

Health authorities expect influenza activity to peak in late December or early January, with test positivity rates potentially reaching around 50% across the European region. The WHO continues to monitor the situation through its Global Influenza Surveillance and Response System (GISRS) network, which operates in 130 countries worldwide.

Dr. Kluge emphasized the importance of preparedness: 'We must strengthen our health systems' readiness ahead of the holiday season when respiratory illnesses typically surge. Even with evolving viruses, our existing tools—vaccination, surveillance, and public health measures—remain our best defense.'

The early onset of this influenza season serves as a reminder of the unpredictable nature of respiratory viruses and the importance of maintaining robust public health infrastructure capable of responding to emerging threats.