Respiratory illness in Sweden
The three major respiratory pathogens side by side — influenza, COVID-19 and RSV — based on ECDC ERVISS weekly data from Folkhälsomyndigheten.
Current situation: Influenza
In week 15 of 2026, activity of influenza (seasonal flu) in Sweden 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 sentinel and virological data from the Public Health Agency of Sweden (Folkhälsomyndigheten); where national indicators are stale, the EU median is used as a fallback. Seasonally, infection waves in Sweden 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 Sweden is low. The trend — derived from clinical surveillance — is stable.
The classification is based on the ECDC ERVISS weekly reports, drawing on COVID-19 indicators from the Public Health Agency of Sweden (Folkhälsomyndigheten); where national indicators are stale, the EU median is used as a fallback. Seasonally, infection waves in Sweden 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 Sweden 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 indicators from the Public Health Agency of Sweden (Folkhälsomyndigheten); where national indicators are stale, the EU median is used as a fallback. Seasonally, infection waves in Sweden 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 Sweden is built on the European Respiratory Virus Surveillance Summary (ERVISS), published weekly by the European Centre for Disease Prevention and Control (ECDC). Folkhälsomyndigheten is the national public-health authority that feeds ERVISS with sentinel primary care and virology data. Sweden does not always report ILI consultation rates to ERVISS; when national ILI is missing we fall back to the EU median so the signal remains comparable.
ECDC ERVISS
ERVISS is ECDC's weekly pan-European surveillance summary for influenza, SARS-CoV-2 and RSV. National authorities — in Sweden's case Folkhälsomyndigheten — 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
Folkhälsomyndigheten 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 Sweden?
Folkhälsomyndigheten combines laboratory-confirmed case notifications, sentinel physician reporting, the Webbsök online signal, and hospital admission data into a weekly respiratory-virus picture covering flu, SARS-CoV-2, and RSV. The same data stream is transmitted to ECDC's ERVISS. The result is a system that describes primary-care and hospital burden, not a raw count of ill people in the community.
Why does respiratory illness peak in Swedish winters?
Swedish winters compound several factors. Dry, cold 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 characteristically prolonged winter plateau rather than a single narrow peak.
How does Sweden compare to other Nordic countries?
Sweden's winter respiratory burden broadly resembles Norway's, Finland's, and Denmark's. Because all four feed ECDC's ERVISS on the same schedule and methodology, the relative intensity and timing of their peaks is easy to read in the European dashboards. Lead–lag patterns between the Nordics are typically small, driven more by school terms and travel than by climate.
How are activity levels classified in Swedish bulletins?
Folkhälsomyndigheten uses qualitative tiers — low, medium, high, very high — derived from historical reference ranges for each indicator. These tiers indicate whether the current week's pressure is ordinary for the season, elevated, or unusually intense. ECDC applies matching tiering so Sweden's classification is directly comparable with the rest of the EU/EEA.
What drives year-to-year variation in Sweden?
Variation comes from the mix of circulating influenza subtypes, residual population immunity, vaccine strain match, SARS-CoV-2 variant dynamics, and RSV circulation — particularly where earlier low-exposure years leave younger cohorts more susceptible. Folkhälsomyndigheten's weekly reports contextualise each season against prior reference periods, which is why qualitative tiering carries more weight than absolute numbers.
Want the actual numbers?
You'll find them in the app.
Here you only see the trend. In the app: exact incidence rates, “X out of 100 people infectious”, your personal risk based on age and pre-existing conditions, wastewater trends, 36 countries, home-screen widget.
