Influenza season has started about 4 weeks earlier than usual in the WHO European Region.
However, this is not out of the ordinary and current trends are similar to those observed in the 2022–2023 influenza season. Influenza activity varies across countries, and some countries in the Region have seen flu cases rising relatively early, while others have not.
Alongside influenza, countries are seeing continued circulation of pathogens such as COVID-19, respiratory syncytial virus (RSV) and others. Together, these viruses reinforce the need for heightened vigilance during the winter months.
Tracking the season: what the data show
WHO conducts year-round surveillance of respiratory illnesses through its Global Influenza Surveillance and Response System, a network of over 170 laboratories worldwide. From early October, Member States intensify reporting so that WHO can determine when the seasonal influenza epidemic has officially begun and monitor its progression.
“Careful monitoring of virus circulation allows health systems to prepare and respond to the annual winter respiratory illness season in the most effective way possible,” explained Dr James Fielding, respiratory virus surveillance lead at WHO/Europe.
As of mid-November 2025, influenza test positivity in primary care (a key indicator of influenza activity) stands at 17% across the Region. Based on previous trends, this season is expected to peak at around 50% positivity in late December or early January.
Why vaccination matters – even when viruses evolve
Influenza evolves constantly, largely driven by the evolutionary pressure of human immunity, through small, incremental changes or mutations. This requires constant monitoring to update the seasonal vaccine. In June 2025, scientists detected an increase in a new H3N2 strain with 7 new mutations, and of a new H1N1 strain, although there are no signs as yet of either causing more severe illness.
Twice a year, the WHO influenza vaccine composition advisory committee reviews global surveillance data to recommend which strains should be included in upcoming vaccines. Although the composition of seasonal influenza vaccines is updated only in February for the northern hemisphere and in September for the southern hemisphere, vaccination remains the most effective way to protect against influenza and its complications.
“Even when circulating influenza virus strains evolve to develop some differences to the vaccine strains, influenza vaccine can still provide meaningful protection against illness, hospitalization and death,” said Marc-Alain Widdowson, Head of the Pandemic Threats, Communicable Diseases and Antimicrobial Resistance unit at WHO/Europe. “It remains really important to get vaccinated – particularly for people at higher risk of severe infection.”
Vaccination also remains vital for COVID-19. A WHO/Europe study showed that vaccines saved an estimated 1.6 million lives in the Region between December 2020 and March 2023. In some countries, RSV vaccines for older adults are also offered; WHO encourages those eligible to take them.
Who is most at risk?
Most severe outcomes from influenza, COVID-19 and RSV occur in:
- older people
- pregnant women
- people with chronic conditions
- immunocompromised people
- infants and young children (particularly for RSV).
Protecting these groups, as well as health workers, remains a top priority.
What can you do to protect yourself and others?
The COVID-19 pandemic demonstrated that simple actions can significantly reduce the spread of respiratory viruses. WHO/Europe urges people to apply these lessons broadly:
- get vaccinated if you are eligible – for influenza, COVID-19 and RSV (where offered);
- stay at home when sick;
- maintain good hand and cough hygiene (sneeze or cough into your elbow);
- improve indoor ventilation wherever possible; and
- if you have symptoms, wear a mask.
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This article was amended on 25 November 2025 to better reflect current public health advice during influenza season.