Respiratory illness in Denmark
The three major respiratory pathogens side by side — influenza, COVID-19 and RSV — in Denmark, based on ECDC ERVISS weekly data from Statens Serum Institut (SSI).
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.
Current situation: COVID-19
In week 15 of 2026, activity of COVID-19 in Denmark is low. The trend — derived from clinical surveillance — is falling.
The classification is based on the ECDC ERVISS weekly reports, drawing on COVID-19 surveillance data from Statens Serum Institut (SSI) via sentinel primary-care surveillance, wastewater monitoring and genomic sequencing. Seasonally, infection waves in Denmark typically peak during winter, with occasional summer waves driven by new variants; activity is usually markedly lower in late spring between waves. How severe a given season becomes depends on the circulating virus variant and the population's immune status, among other factors.
Current situation: RSV
In week 15 of 2026, activity of respiratory syncytial virus (RSV) in Denmark is low. The trend — derived from clinical surveillance — is stable. Over a four-week comparison, a clear decline is visible.
The classification is based on the ECDC ERVISS weekly reports, drawing on RSV surveillance data from Statens Serum Institut (SSI) via sentinel primary-care surveillance, wastewater monitoring and genomic sequencing. Seasonally, infection waves in Denmark typically peak between December and February; activity is usually markedly lower in spring and summer. 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
How is overall respiratory-illness activity tracked in Denmark?
Statens Serum Institut combines mandatory laboratory notifications, sentinel virological testing, hospital and ICU admissions, wastewater detection of SARS-CoV-2, and variant sequencing into a weekly respiratory-virus picture covering flu, SARS-CoV-2, and RSV. Denmark's virological surveillance is among the most intensive in Europe. The same indicators feed ECDC ERVISS. On infectrisk.com we condense this picture into a qualitative low/moderate/high classification.
Did Denmark experience a “tripledemic”?
“Tripledemic” is a media term for the simultaneous winter circulation of flu, COVID-19, and RSV first widely discussed during the 2022–2023 season. Denmark saw clear co-circulation of all three pathogens that winter, with notable pressure on paediatric wards and adult critical care. Co-circulation has recurred each winter since, though the relative intensity of each pathogen varies.
Why do respiratory illnesses peak in a Danish winter?
Danish winters compound several factors. Cold, dry indoor air favours viral stability and impairs mucous-membrane defences. Long, dark months mean extended indoor contact. Flu, RSV, SARS-CoV-2, and a background of rhinoviruses and other endemics often circulate together, producing a prolonged winter plateau rather than a single narrow peak. Danish school terms and travel add additional mixing pulses.
How does Statens Serum Institut decide that activity is “high”?
Statens Serum Institut uses thresholds derived from historical reference data. Current indicators — sentinel consultations, laboratory positivity, hospital admissions, wastewater signals — are compared against baselines from past non-epidemic weeks and against reference points from severe past seasons. When several indicators cross into elevated ranges at once, the weekly bulletin flags activity as high. Denmark's ERVISS contribution uses the same framework for cross-country comparison.
How does Denmark compare to other Nordic countries?
Denmark's winter respiratory burden broadly resembles that of Sweden, Norway, and Finland, though Danish peaks often arrive slightly earlier than Swedish and Finnish ones. Because all four Nordic countries report into ECDC ERVISS on the same schedule and methodology, the relative timing and intensity of their peaks is easy to read in the European dashboards. Lead–lag patterns are typically small, driven more by school terms and travel than by climate.
Want the actual numbers?
You'll find them in the app.
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