Flu season in Finland

Finnish flu activity usually begins rising in late December, peaks between January and March, and fades into April. As in the other Nordic countries, the cold, dark months concentrate indoor contacts and drive winter respiratory transmission. THL — the Finnish Institute for Health and Welfare (Terveyden ja hyvinvoinnin laitos) — publishes weekly influenza updates through its sentinel GP network and National Reference Laboratory. The exact onset and peak shift year to year with the dominant subtypes.

THL describes influenza activity in qualitative phases — baseline, increasing, epidemic, and declining — based on sentinel consultations, laboratory positivity, and severe acute respiratory infection signals from hospitals. These classifications appear in the weekly respiratory-virus bulletin and are also transmitted to ECDC for the European Respiratory Virus Surveillance Summary (ERVISS). The qualitative framing puts each winter in context against previous seasons.

Finland's influenza surveillance combines a sentinel network of primary-care physicians, virological confirmation at the National Reference Laboratory at THL, and hospital notifications of severe cases. Weekly data are integrated into a single respiratory-virus bulletin that covers flu, SARS-CoV-2, and RSV. The same indicators feed ECDC ERVISS, which places Finland's trajectory alongside Sweden, Norway, and the rest of the EU/EEA.

Finland offers free seasonal influenza vaccination to a broad set of groups defined in the national immunisation programme, including children aged six months to six years, older adults, pregnant women, people with chronic illnesses, and healthcare workers. Vaccines are delivered through municipal health centres and occupational-health services. THL publishes vaccine-coverage estimates alongside the weekly surveillance bulletin.

Because Finland reports into ECDC ERVISS with harmonised indicators, its weekly flu classification is directly comparable with Sweden, Norway, Denmark, and Iceland. Nordic countries tend to see broadly similar peak windows between January and March, with lead–lag patterns of a few weeks reflecting school holidays and travel. ECDC's side-by-side dashboards make these cross-country comparisons easy to read.