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Researchers: Not testing for Covid-19 is creating problems
People have become sicker after the pandemic, but without Covid-19 testing it's difficult to understand why.
Several Nordic studies point in the same direction: People are visiting doctors more often, and more are absent from work than before the pandemic. Is this due to after-effects of Covid-19, or something entirely different?
A new study from the Norwegian Institute of Public Health shows that in 2024, concultations with GPs and emergency rooms were more than seven per cent higher than the pre-pandemic trend would suggest.
That amounts to around 1.2 million additional doctor visits compared to what would have been expected based on the period from 2010 to 2019.
The increase is seen across all age groups, particularly for respiratory infections, fatigue, psychological symptoms, and cognitive issues such as memory loss.
Is it really about Covid-19?
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One of those who believes that after-effects of Covid-19 are a possible explanation for the increase is Richard Aubrey White. He is a senior researcher at the Norwegian Institute of Public Health and the lead author of the study.
Many people have had Covid-19 multiple times, and each infection carries a risk of long-term effects. Research also suggests that repeated infections may affect the immune system, he notes.
The registry data used in the study mainly shows what people contact a doctor for. It provides little information about who has actually had Covid-19 and how many times. As a result, the researchers cannot conclude a cause-and-effect relationship.
The increase in doctor visits may be due to long-term effects of Covid-19. But it could also be influenced by other factors, such as long-term consequences of restrictions during the pandemic, economic uncertainty, and rising living costs – or that people simply go to the doctor more than before, White points out.
Sweden provides some more answers
In Sweden, researchers have been able to follow individuals before and after a Covid-19 infection and compare them with people who were never infected.
Before the pandemic, both groups showed similar patterns in how they used healthcare services.
"After Covid-19, we saw an increase of 33 additional healthcare contacts per 100 infected people compared to those who were not infected," says Maria Bygdell.
She is the lead author of a new study from the University of Gothenburg, published shortly before the new year.
The Norwegian study shows that the healthcare system is experiencing broad pressure after the pandemic. In Sweden, researchers see that a smaller group of patients accounts for most of the increase – about five per cent of people who have had Covid-19.
"The diagnoses that increased the most are typical for long Covid, including fatigue," says Bygdell.
The Swedish registry data covers around 40 per cent of the population and the two largest regions in the country, she explains.
Around 1.5 million people participated in the study. This included both people who had previously tested positive for Covid-19 and people who had not. During the study period, more than 750,000 participants tested positive for Covid-19 for the first time.
Those who became seriously ill struggle the most
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A European study of 250,000 adults shows that the risk of long-term health problems is highest among those who became seriously ill from Covid-19.
Those who were bedridden for more than one week had nearly twice the risk of depression compared to the rest of the population. The problems lasted a long time, up to 16 months after infection.
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Researchers interpret this as suggesting that having had Covid-19 does not automatically lead to mental health problems. It depends on how sick you become.
Sick leave has increased
Most European countries have had a rise in sick leave after the pandemic. This also applies to Norway, according to another study from the Norwegian Institute of Public Health.
The increase is particularly linked to respiratory infections, mental health diagnoses, and fatigue.
"But when we compare total sickness absence in Norway with other European countries, Norway seems to stand out. It keeps getting worse year after year," says lead author Richard Aubrey White.
He believes there are several possible explanations for this.
The population may actually have become sicker.
It may also reflect that sick leave in Norway better mirrors actual health conditions, because people are more likely to stay home when ill than in some other countries.
White also believes that Norwegian policies may negatively affect health and sickness absence. He stresses that he is not speaking on behalf of his employer, the Norwegian Institute of Public Health.
White argues that Norway's coronavirus strategy relies on repeated and frequent infections in order to maintain immunity in the population, as described in the institute's status report (link in Norwegian).
"The costs linked to long-term consequences, such as long Covid, have not been included in the assessments. Neither the strategy nor the authorities' risk assessments mention long Covid," he points out.
"Long Covid appears to be serious"
Arne Søraas, head of the Corona Study at Oslo University Hospital, shares White's concern.
The study followed nearly 200,000 adults in Norway during and after the pandemic. The participants, both those who have tested positive and those who have not, answered online questionnaires.
"Our findings show that long Covid appears to be serious," says Søraas.
Researchers found a clear increase in cognitive problems among those who had Covid-19 compared with a control group. People who have been infected report persistent problems with memory and concentration.
"More recent studies also suggest that repeated infections may have an 'additive' effect. Both we and other researchers see that the risk increases slightly each time," says Søraas.
He therefore believes that the authorities should do more to limit infection.
"Population data on mortality, sick leave, and diagnoses show trends that are consistent with findings from long Covid research. The patterns are so clear that they have to be taken seriously," he says.
READ ALSO: Is it dangerous to get Covid-19 multiple times?
Sharp rise in mental health diagnoses
Tobias Lunde, a researcher at the Norwegian Labour and Welfare Administration, has contributed to a study showing a steep rise in mental health diagnoses in the sickness absence statistics from 2018 to 2023.
He says the increase is difficult to explain.
"The increase is quite sudden and affects the entire population. That allows us to rule out many explanations that apply only to specific groups," he says.
Lunde finds it striking that the increase coincides with the pandemic.
"Finnish researchers have also found something similar. In Finland, nearly the entire population appears to face a higher risk of receiving a mental health diagnosis after the pandemic," he says.
"Striking how little we know"
Lunde believes it is possible that long Covid plays a role.
"But we don't know. We also don't know whether the population's mental health has worsened, and whether that alone could explain the increase," he says.
Lunde adds that Covid-19 testing is no longer carried out systematically in Norway, meaning researchers do not know who has actually been infected.
"At the same time, there's a lack of systematic monitoring of mental health in the general population," he says.
Because of these gaps, much of the debate about how much of the increase in sick leave can be explained by long Covid and mental health problems becomes speculative, Lunde argues.
"It's actually striking how little we know about such a serious problem," says Lunde.
"Very few try to bridge the gap"
Nina Langeland is a professor at the University of Bergen and a senior physician at Haukeland University Hospital, where she researches long Covid.
She agrees that the current knowledge base is limited, but stresses that long Covid is also difficult to study properly.
"If you ask people directly and follow them over time, more will report symptoms of long Covid. Then the prevalence becomes higher," she explains. " But if you only rely on diagnostic codes from hospitals and general practitioners, you only capture the people who actually seek medical care – and where the doctor also suspects a link to Covid. That gives lower numbers."
Langeland explains that different methods give different answers. No single method provides the full picture.
She calls for more detailed clinical studies, where function, blood tests, MRI, and other examinations are linked to population and registry data.
"Researchers today tend to operate in isolated spheres, each with their own perspectives and approaches. Very few try to bridge the gap between the different research methods," she says.
The problem of not testing
Maria Bygdell in Sweden points out that registry-based research on long Covid has become challenging after the pandemic.
"Covid testing has declined. We can therefore no longer be sure who has had Covid-19. That creates methodological problems," she says.
Richard White agrees.
"When very few people test, it becomes much harder to link symptoms to Covid-19," he says.
General practitioners in Norway, for example, have no specific diagnostic code for long-term effects of Covid-19. Instead, they have to rely on symptom-based codes like 'fatigue.'
"Without a positive test, patients may instead be registered with 'burnout,' which is a mental health diagnosis. That means some long-term effects of Covid-19 may be misregistered as psychiatric disorders," says White.
Why not find out what the patient actually has?
Nina Langeland says that as an infectious disease specialist, she finds it hard to understand why there is almost no testing for respiratory infections today.
"One of the few genuinely positive outcomes of the pandemic was better and faster tests. The technology exists – it's reliable and cheap. So why wouldn't we use it to determine what the patient is actually suffering from?" she asks.
"Testing can also help people protect vulnerable family members – whether we're talking about acute illness or possible long-term consequences," says Langeland.
Arne Søraas points out that almost all Western countries still encourage measures aimed at breaking chains of infection.
"Some of the countries with the most successful strategies recommend testing and self-isolation if you have Covid-19," he says.
He notes that reducing spread means fewer people get sick – and fewer develop long-term effects.
"We want Covid-19 as rarely as possible," he says.
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Translated by Alette Bjordal Gjellesvik
Read the Norwegian version of this article on forskning.no
References:
Bygdell et al. Change in healthcare utilization before and after COVID-19 using data from 1.5 million individuals, Journal of Internal Medicine, vol. 299, 2026. DOI: 10.1111/joim.70051
Magnúsdóttir et al. Acute COVID-19 severity and mental health morbidity trajectories in patient populations of six nations: an observational study, Lancet Public Health, 2022. DOI: 10.1016/S2468-2667(22)00042-1
White et al. Aberrations in medically certified sick leave and primary healthcare consultations in Norway in 2023 compared to pre-COVID-19-pandemic trends, Archives of Public Health, vol. 82, 2024. DOI: 10.1186/s13690-024-01411-4
White et al. Excess primary healthcare consultations in Norway in 2024 compared to pre-COVID-19-pandemic baseline trends, Archives of Public Health, 2026. DOI: 10.1186/s13690-025-01817-8
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