Flu season in Belgium
Current flu, COVID-19 and RSV activity in Belgium — based on ECDC ERVISS weekly data from Sciensano. 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 Belgium 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 data from Sciensano via its sentinel GP network and the National Reference Centre for Influenza. Seasonally, infection waves in Belgium typically peak between December and February; 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 Belgium is built on the European Respiratory Virus Surveillance Summary (ERVISS), published weekly by the European Centre for Disease Prevention and Control (ECDC). Sciensano via its sentinel GP network and the National Reference Centre for Influenza is the national public-health authority that feeds ERVISS with sentinel primary care and virology data.
ECDC ERVISS
ERVISS is ECDC's weekly pan-European surveillance summary for influenza, SARS-CoV-2 and RSV. National authorities — in Belgium's case Sciensano via its sentinel GP network and the National Reference Centre for Influenza — 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
Sciensano via its sentinel GP network and the National Reference Centre for Influenza 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 Belgium?
Belgian flu activity usually builds through December, peaks between December and February, and eases by April. Timing and intensity depend on the dominant influenza subtypes and residual immunity. Sciensano, Belgium's national public-health institute in Brussels, publishes weekly influenza updates describing the season in qualitative phases rather than precise onset dates.
How does Sciensano classify flu severity?
Sciensano classifies flu activity in qualitative bands — baseline, low, moderate, high, very high — drawing on its sentinel GP network, sentinel laboratories, and hospital surveillance for severe acute respiratory infection. Each week's classification is compared with historical reference ranges. Sciensano also transmits Belgian indicators to ECDC ERVISS, which places them alongside other EU/EEA countries using harmonised tiering.
How is flu surveillance organised in Belgium?
Belgian flu surveillance combines a sentinel network of general practitioners reporting weekly influenza-like illness consultations, sentinel laboratories testing respiratory samples for influenza subtypes, and hospital surveillance of severe acute respiratory infection. The National Reference Centre for Influenza, hosted at Sciensano, performs virological characterisation. Results feed Sciensano's weekly respiratory-virus bulletin and ECDC ERVISS.
Is the flu vaccine reimbursed in Belgium?
Belgium's Conseil Supérieur de la Santé / Hoge Gezondheidsraad recommends annual flu vaccination for priority groups including adults aged 65 and above, pregnant women, people with chronic conditions, residents of long-term-care facilities, and healthcare workers. The vaccine is partially reimbursed by the INAMI/RIZIV for these groups. Sciensano publishes vaccination-coverage estimates alongside its weekly flu surveillance.
How does Belgium compare to its European neighbours?
Because Belgium reports into ECDC ERVISS with harmonised indicators, its weekly flu classification is directly comparable with France, the Netherlands, Luxembourg, and the rest of the EU/EEA. Belgium sometimes sees flu activity pick up slightly earlier than its western European neighbours, though lead–lag differences of a few weeks are typical and visible in ECDC's dashboards.
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