Flu season in Denmark
Current flu, COVID-19 and RSV activity in Denmark — based on ECDC ERVISS weekly data from Statens Serum Institut (SSI). Rescaled into a consultation-equivalent signal for a qualitative low / moderate / high classification.
Current situation: Influenza
In week 15 of 2026, activity of influenza (seasonal flu) in Denmark is low. The trend — derived from clinical surveillance — is falling. Over a four-week comparison, a clear decline is visible.
The classification is based on the ECDC ERVISS weekly reports, drawing on data from Statens Serum Institut (SSI) via sentinel primary-care surveillance, wastewater monitoring and genomic sequencing. Seasonally, infection waves in Denmark typically peak between January and March; activity is usually markedly lower during the summer months. How severe a given season becomes depends on the circulating virus variant and the population's immune status, among other factors.
Data sources and methodology
The current picture for Denmark is built on the European Respiratory Virus Surveillance Summary (ERVISS), published weekly by the European Centre for Disease Prevention and Control (ECDC). Statens Serum Institut (SSI) is the national public-health authority that feeds ERVISS with sentinel primary care and virology data. Denmark combines sentinel primary-care surveillance with wastewater monitoring and genomic sequencing, so the ERVISS signal for Denmark is especially well-triangulated.
ECDC ERVISS
ERVISS is ECDC's weekly pan-European surveillance summary for influenza, SARS-CoV-2 and RSV. National authorities — in Denmark's case Statens Serum Institut (SSI) — submit harmonised indicators every week, which ECDC publishes in a standardised dataset on Thursdays. Using ERVISS rather than each country's native portal ensures cross-country comparability.
ILI / ARI consultation rates and positivity
Statens Serum Institut (SSI) operates a sentinel network of general practices that report weekly rates of patients consulting for influenza-like illness (ILI) or acute respiratory infection (ARI). A subset of patients is swabbed and tested by reference laboratories, producing pathogen-specific positivity rates for flu, SARS-CoV-2 and RSV.
Why this source
Combining consultation incidence with virological positivity yields a pathogen-specific weekly incidence signal (ILI × positivity / 100). This is the standard European methodology and provides a more robust view than either indicator alone — consultation rates capture illness burden, positivity confirms which pathogen is driving it.
Qualitative classification
The “low”, “moderate” and “high” categories follow seasonal reference values and epidemiological thresholds calibrated to match our classifications for other countries. The ILI × positivity / 100 product is scaled to comparable thresholds using a divisor of 3, which aligns European sentinel peaks with the consultation-equivalent scale used elsewhere. Data refreshes weekly when ECDC publishes the latest ERVISS update, typically on Thursdays.
Frequently asked questions
When is flu season in Denmark?
Danish flu seasons typically build through December, peak between January and March, and fade by April. The exact window shifts each year with the dominant influenza subtypes and residual population immunity. Statens Serum Institut (SSI) describes the season in qualitative phases through its weekly Ugentlige Overvågningsrapporter rather than precise onset dates, and Denmark's Nordic latitude means peaks often arrive slightly later than in central Europe.
How does Statens Serum Institut classify flu severity?
Statens Serum Institut uses qualitative tiers — low, medium, high, very high — derived from historical reference ranges for sentinel consultations, laboratory positivity, and hospital indicators. These tiers reflect whether the week's pressure is ordinary, elevated, or exceptional for the season. SSI also transmits Denmark's indicators to ECDC for inclusion in ERVISS, where Danish classifications sit alongside other EU/EEA countries with the same methodology.
How is flu surveillance organised in Denmark?
Denmark's flu surveillance combines a sentinel network of general practitioners reporting influenza-like illness, a dense virological testing programme coordinated by Statens Serum Institut, and hospital-admission data for severe acute respiratory infection. Denmark has one of the most comprehensive virological surveillance programmes in Europe, with extensive sequencing of respiratory samples. Weekly bulletins summarise the picture and feed ECDC ERVISS.
Is the flu vaccine free in Denmark?
Denmark offers free seasonal flu vaccination each autumn to priority groups including adults aged 65 and above, pregnant women, people with chronic conditions, and healthcare workers, administered through GPs and participating pharmacies. Statens Serum Institut publishes vaccination-coverage estimates alongside its weekly flu surveillance reports. Uptake in Danish older-adult groups is historically among the higher ranges in the EU.
How does Denmark compare to other Nordic countries?
Because Denmark reports into ECDC ERVISS with harmonised indicators, its weekly flu classification is directly comparable with Sweden, Norway, Finland, and the rest of the EU/EEA. Nordic flu curves typically move broadly in step, with small lead–lag differences driven by school calendars and travel patterns. Denmark often peaks a little earlier than Sweden and Finland, though this varies by season.
Want the actual numbers?
You'll find them in the app.
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