Flu season is on the way.
It’s difficult to predict just how severe the influenza season will be each year, but public health experts say it could be harsh in Europe due to lagging vaccination rates and early signals from far-flung countries such as Japan and Australia.
As of mid-October, the number of patients with flu-like respiratory symptoms “remains low but is increasing in most countries, as expected for this time of year,” according to the European Centre for Disease Prevention and Control (ECDC), which tracks flu activity in the European Union, Iceland, Liechtenstein, and Norway.
Europe’s flu season usually runs from mid-November to late May – but seasonal patterns may have shifted since the COVID-19 pandemic.
After a shorter-than-usual flu season from 2023-2024, last year’s season was “unusually large,” Colin Russell, a professor at Amsterdam University Medical Center and chair of the European Scientific Working Group on Influenza (ESWI), told Euronews Health.
Eleven countries are now reporting sporadic flu activity, ECDC data shows. Meanwhile, in the United Kingdom, health officials have warned that flu levels are already rising, particularly among children.
“It’s the time of the year where everything starts,” Dr Anna Odone, director of the School of Public Health at the University of Pavia in Italy, told Euronews Health.
Ultimately, Odone said the season’s severity in any given country will depend on three factors: the number of vulnerable people, the strain of the virus spreading this year, and the environment. For example, if it’s a long, cold winter, people may spend more time indoors, allowing the virus to spread more easily.
Health experts are now watching for signs of early flu outbreaks in places where people have close contact with each other – such as schools, elderly care facilities, and prisons – to determine when the flu season really starts. That can differ based on the country.
Officials are also monitoring which strains of the flu crop up. Last year, the H1 and H3 strains of influenza A, along with influenza B/Victoria, were the primary strains in much of Europe.
Other parts of the globe could offer some clues. In Australia and New Zealand, a strain of influenza A, called H3N2, has surged over the past two months, around the end of winter. Meanwhile, Japan declared an influenza epidemic earlier this month, some five weeks earlier than the flu season usually starts there.
However, it is too soon to say with certainty which strains will be dominant in Europe this year.
“We’re in wait-and-see mode right now,” Russell said.
Influenza risks tied to vaccination
While the flu doesn’t usually cause serious health problems for young, healthy people, it is a simmering threat during the colder months alongside other respiratory illnesses, such as respiratory syncytial virus (RSV), pneumonia, and COVID-19.
Up to one in five Europeans is infected with influenza every winter, and it is associated with about 27,600 deaths annually across the EU.
Getting vaccinated ahead of flu season is the best way to protect against the virus and relieve pressure on hospitals. The jab is updated every year because protection from the vaccine weakens over time, likely due to a combination of waning immunity and the influenza virus evolving.
Yet vaccination rates have lagged across Europe in recent years for both influenza and routine childhood vaccines, which an ECDC spokesperson described as “a cause for concern”.
The shift away from vaccines could make the upcoming flu season harsher.
The EU flu vaccination coverage target is 75 per cent, but during the last flu season, most countries reported coverage “well below” 50 per cent, according to the ECDC. The highest levels were reported in Denmark (76 per cent), Ireland (75 per cent), Portugal (71 per cent), and Sweden (68 per cent).
“Immunisation has social and political connotations … so it’s not really easy to get high coverage rates, which is what we need to control influenza,” Odone said.
The ECDC spokesperson told Euronews Health that local officials should work to “strengthen public trust, improve access, and ensure that parents and caregivers are well-informed about the importance of timely vaccination”.
Health experts say vaccination is particularly important for high-risk groups, including people with certain chronic conditions, pregnant women, children aged six months to five years, older adults, and health care workers. Most countries issue specific guidelines for higher risk groups.
Russell said these people should get vaccinated as close as possible to the beginning of the flu season, and not wait until the virus is already circulating widely. It takes about two weeks after being vaccinated for your body to develop protection against the flu.
While the start of the European flu season could vary depending on where you are on the continent, “the easy answer is, if you’re not vaccinated yet, you should go get vaccinated now,” Russell said.