The complaints rotated but the total burden of feeling sick stayed flat.
Five years after a virus reshaped the world, a long and patient Dutch study has offered something rare in the history of pandemics: a measured account of how an extraordinary threat becomes ordinary. Tracking nearly 38,000 volunteers over four and a half years, researchers found that COVID-19 has settled into an endemic rhythm comparable to seasonal influenza — not vanished, not harmless, but knowable. The transition arrived faster than most models predicted, and with it comes the quiet relief of predictability replacing chaos.
- A signature symptom of the early pandemic — the eerie loss of smell and taste — has largely faded, replaced by the familiar misery of sore throats and congestion, signaling a virus that has changed its face without loosening its grip.
- The most unsettling finding is what didn't improve: despite widespread immunity, the total burden of feeling sick during a COVID episode has not declined since late 2022, defying the expectation that a population grows progressively more resilient.
- Millions of people who never needed a hospital bed but still missed work, felt genuinely unwell, and endured days of disruption had gone largely uncounted — this study finally puts numbers to their experience.
- When stacked against seasonal flu data from the same Dutch population, COVID's endemic form matched influenza in illness duration, work absences, and perceived health impact — a middle ground between a cold and a crisis.
- Healthcare systems now have a stable target: COVID can be planned for like flu, with consistent vaccine strategies and recovery guidance, replacing years of reactive scrambling with something resembling foresight.
Five years into the pandemic, a Dutch research team has produced one of the most granular records of how COVID actually disrupts ordinary lives. Epidemiologist Gesa Carstens and colleagues at the Dutch National Institute for Public Health and the Environment ran a public surveillance project for four and a half years, enrolling nearly 38,000 volunteers who logged symptoms weekly and submitted self-tests when ill. Of those, 18,600 reported at least one positive result between late 2020 and early 2025. What emerged was a portrait of a virus that changed its symptoms while holding its weight.
In the early years, infected people described losing their sense of smell or taste, suffering exhausting fatigue, and enduring persistent headaches. By the later years of the study, those complaints had given way to sore throats, runny noses, and congestion — the familiar vocabulary of a respiratory season. The virus had not disappeared; it had simply registered differently.
What surprised the researchers most was the plateau. Conventional epidemiological wisdom holds that as immunity spreads, infections should feel progressively milder. The Dutch data disagreed. From late 2022 onward, the average health score during a COVID episode held steady. The proportion of people experiencing ten or more symptoms at once did not fall. The specific complaints rotated, but the total burden of being sick remained flat — a finding that had eluded researchers focused primarily on hospitalizations and deaths.
When compared to seasonal influenza in the same population, the parallels were striking: similar illness durations, comparable work absences, and an equivalent drag on self-perceived health. The authors concluded that COVID, in its endemic phase, now occupies a middle ground closer to flu than to a common cold — and the data suggests it will stay there.
The speed of this transition surprised even the researchers. Some models had projected that a stable endemic pattern might take decades to emerge; the Dutch data show it had already arrived by late 2022, roughly three years after the virus first appeared. The study has limits — volunteers tend to be more health-conscious than average, all symptoms were self-reported, and long COVID falls outside its scope — but its longitudinal depth is difficult to match.
The practical implications are considerable. Hospitals can plan for a predictable respiratory burden. Doctors can offer familiar recovery timelines. Vaccine programs can target consistent high-risk groups rather than recalibrating each season. Endemic does not mean harmless — COVID continues to cost people days of work and genuine wellbeing. But that cost has stabilized, and after five years of uncertainty, stability itself is a form of progress.
Five years into the pandemic, a Dutch research team has documented something that was hard to measure before: how COVID actually disrupts the lives of ordinary people who catch it. For 4.5 years, epidemiologist Gesa Carstens and her colleagues at the Dutch National Institute for Public Health and the Environment ran Infectieradar, a public surveillance project where volunteers logged in weekly to report symptoms, took self-tests when they felt sick, and sent in nose swabs when asked. Nearly 38,000 people participated. Of those, 18,600 reported at least one positive test between November 2020 and April 2025. What emerged from this continuous, granular record was a portrait of how a virus can change its face while keeping its weight.
In the early pandemic years, people infected with COVID described losing their sense of smell or taste. They reported the kind of exhaustion that kept them in bed for days, along with headaches that made thinking difficult. By the later years of the study, the symptom profile had shifted noticeably. Sore throats, runny noses, and congestion became the dominant complaints. The loss of smell and taste, once a signature marker of infection, faded into the background. The virus had not disappeared. It had simply registered differently in the bodies of infected people.
What surprised the researchers most was what did not change. A common expectation in epidemiology is that as immunity spreads through a population, infections should feel progressively milder—fewer symptoms, fewer doctor visits, less disruption to daily life. The Dutch data told a different story. From late 2022 onward, the average health score people reported during a COVID episode remained stable. The proportion of people experiencing more than ten symptoms at once did not decline. The specific complaints rotated, but the total burden of feeling sick stayed flat. This plateau was the piece of the puzzle that had eluded researchers before. Most previous studies had focused on hospitalizations and deaths—numbers that did drop sharply once vaccination rates climbed. What happened to the millions of people who stayed home sick, who missed work, who felt genuinely unwell but never needed a hospital bed, remained largely unmeasured until now.
When the team compared their findings to the impact of seasonal influenza in the same Dutch population, the parallels were striking. COVID and flu produced similar illness durations. Both caused comparable absences from work. Both created a similar drag on how people perceived their own health. The authors concluded that the health burden of COVID, in its endemic phase, now sits closer to influenza than to other common respiratory infections. It is not the picture of an ordinary cold, and it bears no resemblance to the early pandemic. It occupies a middle ground, and the data suggests it will remain there.
The speed at which this transition occurred caught some researchers off guard. A 2021 modeling paper had projected that COVID would eventually settle into a stable pattern, possibly resembling one of the four other human coronaviruses already circulating in the population. When this would happen was uncertain—some forecasts suggested it might take decades. Carstens's data show that in the Netherlands, a stable endemic pattern had already emerged by late 2022, roughly three years after the virus first arrived. This was faster than even the most optimistic models had predicted.
The researchers are careful about the limits of their work. Volunteers in surveillance projects tend to be more health-conscious than the general population. All symptoms were self-reported, not measured in a clinical setting. The study cannot speak to long COVID, the condition that sometimes emerges months after an acute infection has resolved. What the data can do exceptionally well is track how a typical bout of COVID has changed over a long stretch of time, week by week, in a way that few other studies have managed.
The practical implications are significant. Hospital systems can now plan for a respiratory illness that behaves, in terms of disease burden, more like flu than like a cold. Doctors can give patients recovery timelines that feel familiar rather than unprecedented. Vaccine recommendations can target the same high-risk groups year after year, rather than scrambling to recalibrate each season for a moving threat. Endemic does not mean harmless. The Dutch findings make that abundantly clear. COVID continues to disrupt work, to make people feel genuinely sick, to impose a measurable cost on daily life. What has changed is that this cost has stabilized at a level comparable to seasonal influenza, and it has remained stable for years. After five years of uncertainty, the ability to track this in real numbers represents a shift from chaos to something resembling predictability.
Citas Notables
The health impact of COVID now sits closer to flu than to other common respiratory infections— Gesa Carstens and co-authors, published in Lancet Microbe
La Conversación del Hearth Otra perspectiva de la historia
So the study tracked nearly 40,000 people for four and a half years. That's an unusual commitment. What made them stick with it?
They were answering a simple question every week: Are you sick? If yes, what symptoms? It wasn't burdensome. And the people who signed up tended to care about their health anyway. That self-selection matters—it means the data skews toward people paying attention, not the full population.
The shift from loss of smell and taste to sore throats—that's a real change in the virus, or just how people experience it differently now?
Probably both. The virus itself may have evolved. But immunity also matters. When you've been vaccinated or infected before, your immune system meets the virus differently. You might not lose your sense of smell because your body catches it earlier, in the upper airways, before it goes deeper.
The plateau is the surprising part, right? Symptoms changed but the total burden didn't lighten?
Yes. That's what nobody expected. The assumption was that as immunity built up, people would just feel less sick overall. Instead, the complaints rotated but the weight stayed the same. People still missed work. They still felt genuinely unwell. It just looked different.
How does that compare to flu?
Duration, work absences, how sick you feel—all similar now. Not identical, but in the same ballpark. That's useful information for hospitals and doctors. They can plan around something familiar.
Did the speed surprise them? Three years to endemic status?
Yes. Models from 2021 suggested it might take much longer, possibly decades. The Netherlands hit a stable pattern by late 2022. That's faster than the gentlest predictions.
What about long COVID? Does this study tell us anything about that?
No. Long COVID plays out over months, sometimes longer. This study captures the acute infection—the week or two when you're actively sick. Long COVID is a different timeline, a different question.