More severe cases than last year seems inevitable
Each winter, the flu returns to test the resilience of communities and the wisdom of their preparations — and this January, Spain finds itself in a familiar but sobering position. The epidemic is accelerating toward its expected peak in late January, with incidence rising sharply in a single week and hospitals feeling the strain, while vaccination rates fall short of what would shield the most vulnerable. The virus itself is unremarkable; what is remarkable, and troubling, is the gap between the protection available and the protection taken.
- Flu cases in Spain surged from 42.2 to 62.6 per 100,000 inhabitants in just one week, with hospitalizations nearly doubling in the same period as the epidemic crosses into its most dangerous phase.
- The dominant strain has shifted from the milder flu B to flu A, which historically drives the highest peaks and the most severe illness, raising the stakes for an already strained healthcare system.
- Experts warn that low vaccination rates — below last year's already insufficient levels — leave the elderly, chronically ill, and immunocompromised especially exposed, with more severe cases and deaths expected as a result.
- A major multinational study of 6.5 million patients found that flu vaccination cuts mortality risk in half, yet the season is unfolding with fewer people protected than at any point in recent years.
- The epidemic's peak is expected in two to three weeks, with the wave likely extending through March, as Spain returns to pre-pandemic flu seasonality after years of COVID-disrupted patterns.
Spain's flu epidemic is climbing sharply toward what experts believe will be its peak in late January. In just one week, the incidence rate jumped from 42.2 to 62.6 cases per 100,000 inhabitants, while hospitalizations nearly doubled over the same period. Epidemiologist Quique Bassat and infectious disease specialist José María Molero both place the worst of the season two to three weeks away, with the epidemic likely extending through March — a timeline that reflects Spain's return to pre-pandemic flu patterns after years of disruption caused by COVID-19.
The nature of the virus circulating has also shifted. Flu B dominated the early weeks of the season, but it has been steadily replaced by flu A, the strain associated with more severe illness and higher peaks. José María Eiros, director of Spain's National Influenza Center in Valladolid, cautioned that no two flu seasons are identical — the virus can produce multiple waves — but the data points clearly toward continued escalation. Epidemiologist Ángela Domínguez added that this week's figures, gathered during the holiday period when many people were away from their regular doctors, likely undercount actual cases; next week's data should offer a clearer picture.
What worries experts most is not the virus itself, which Bassat described as presenting very classic symptoms — cough, fever, malaise, sore throat, congestion — with no unusual severity. The concern is the population's defenses. Vaccination rates are lower than last year, which were already below target levels. A new study published in the European Respiratory Review, drawing on data from more than 38 countries and 6.5 million patients, found that flu vaccination cuts the risk of death in half and reduces the likelihood of serious complications including pneumonia and ICU admission. Yet fewer people are protected this year, particularly among the elderly and immunocompromised — the groups most at risk. Spain's healthcare system now faces rising case numbers and a population less shielded than it should be.
Spain is watching its flu epidemic climb toward what experts believe will be its worst point in roughly two to three weeks, sometime in late January. The numbers tell the story of acceleration: in just seven days, the incidence rate jumped from 42.2 cases per 100,000 inhabitants to 62.6. Hospitalizations are climbing too, rising from 2.5 to 4.7 cases per 100,000 in the same period. The virus has crossed what epidemiologists call the epidemic threshold, and the strain on hospitals is intensifying as the season enters what should be its most dangerous phase.
What makes this year different is timing. The flu arrived later than it has in the past two or three years, returning Spain to what epidemiologists call pre-pandemic patterns. When COVID-19 arrived, it disrupted the normal seasonal rhythm of influenza entirely, pushing the virus into unusual windows and creating unexpected waves. Now, after years of disruption, the flu is behaving more like it used to. Quique Bassat, an epidemiologist and pediatrician, explained to reporters that the virus is moving into its strongest phase, but the real peak—the moment when cases will likely reach their maximum—should arrive in two or three weeks. José María Molero, an infectious disease specialist, agreed on the timing and added that the epidemic will probably extend all the way through March.
The character of the virus itself has shifted. The season began with flu B circulating widely, but over the past month that strain has been declining and being replaced by flu A, which tends to cause more severe illness. Flu A is the strain typically responsible for the highest peaks and the most infections. José María Eiros, who directs Spain's National Influenza Center in Valladolid—an institution that has tracked the virus for four decades—cautioned that predicting the exact shape of any flu season is difficult. "There are no two identical flu seasons," he said. Sometimes the virus produces two separate waves with quiet periods between them. But based on what the data shows now, activity will almost certainly increase.
The numbers reported this week come from the first week of the year, when much of Spain's population was traveling during the holidays and away from their regular doctors. This means the figures may not capture the full picture. Ángela Domínguez, who coordinates the vaccine group at Spain's Epidemiological Society, suggested that next week's data—collected after people returned from holiday—will offer a more reliable snapshot of what is actually happening.
What concerns experts most is not the virus itself but the population's defenses against it. Vaccination rates this year are lower than they were last year, and last year's rates were already below target levels. Molero warned that this means Spain should expect more severe cases than it saw in the previous season. A new study published this week in the European Respiratory Review, conducted by researchers from CEU San Pablo University, the Carlos III Health Institute, the National Influenza Center, and Madrid's Hospital 12 de Octubre, analyzed data from more than 38 countries and 6.5 million patients. The research found that flu vaccination cuts the risk of death in half. The protection varies by age group and virus subtype, but the vaccine is highly effective at preventing death regardless of which flu strain infects a person. For those who do get sick despite vaccination, the shot reduces symptom severity and the likelihood of serious complications like pneumonia, ICU admission, and hospitalization.
Yet fewer people are protected this year. The virus itself appears typical—no more severe than previous years. The most common symptoms remain the same: cough in 80.6 percent of cases, fever in 74.8 percent, general malaise in 72.5 percent, sore throat in 61 percent, and nasal congestion in 60.7 percent. Bassat noted there is nothing in the data suggesting this year's virus behaves differently from others. "It is a very classic flu with the most typical symptoms," he said. The danger lies not in the virus being worse but in fewer people being vaccinated against it, particularly among the elderly, those with chronic illnesses, and immunocompromised individuals who face the highest risk of severe disease. As the epidemic enters its steepest climb, Spain's healthcare system will face the dual challenge of rising case numbers and a population less protected than it should be.
Notable Quotes
The flu is now entering its strongest phase, with the real peak arriving in two to three weeks— Quique Bassat, epidemiologist and pediatrician
We should expect more severe cases than last year, unfortunately, because vaccination protection is fundamental— José María Molero, infectious disease specialist
The Hearth Conversation Another angle on the story
Why did the flu arrive later this year than in recent seasons?
COVID disrupted everything. When the pandemic hit, it pushed other respiratory viruses into unusual patterns. Now that COVID is no longer dominant, the flu is returning to its old rhythm—which happens to be later in the winter than we saw during those disrupted years.
So the peak is still ahead of us?
Yes. We're in early January and experts expect the worst of it in late January or early February. The virus is shifting from type B to type A right now, and type A is what usually causes the highest peaks and the most hospitalizations.
What worries the doctors most?
Not the virus itself—they say it's behaving like a normal flu. What worries them is vaccination. Fewer people are vaccinated this year than last year, and last year was already below where it should be. That means more people will get severely ill.
How much does the vaccine actually help?
A new study of 6.5 million patients across 38 countries found it cuts the death risk in half. Even when vaccinated people do get sick, they have milder symptoms and fewer complications.
Who is most at risk right now?
The elderly, people with chronic diseases, and anyone with a weakened immune system. These groups face the highest chance of severe illness or death, and they're the ones least protected if vaccination rates stay low.
What happens if the peak arrives as predicted?
Hospitals will be under real strain. Hospitalizations are already rising. If the numbers climb as expected and people aren't vaccinated, you'll see more ICU admissions, more pneumonia cases, more deaths—all preventable with a shot.