What's going around in Poland?

NIZP PZH combines primary-care reports of influenza-like illness and acute respiratory infection with laboratory results for influenza, SARS-CoV-2, and RSV. These streams are aggregated into weekly bulletins and transmitted to ECDC's ERVISS. Together they describe the burden carried by doctors' surgeries and hospitals, rather than a raw count of everyone who is ill at home, consistent with how other European surveillance systems work.

Several factors stack during Polish winters. Cold, dry indoor air favours viral stability and weakens mucous-membrane defences. People spend more time indoors in poorly ventilated spaces. School terms and indoor gatherings intensify mixing. And several respiratory viruses (flu, RSV, SARS-CoV-2, plus rhinoviruses and other endemics) tend to circulate simultaneously, which compounds the overall load.

Poland's winter respiratory burden is broadly comparable to central and eastern European neighbours, though peaks often lag Germany and Austria by a few weeks. Because all EU/EEA countries feed ERVISS, ECDC produces side-by-side visualisations that make relative intensity and timing easy to read. This cross-border view is one of the main reasons ECDC's platform exists.

NIZP PZH uses qualitative tiers (baseline, low, moderate, high, very high) derived from historical reference ranges for ILI/ARI consultation rates and laboratory positivity. These tiers are designed to show whether current pressure is ordinary, elevated, or unusually intense for the time of year. They deliberately avoid implying false precision in the underlying sentinel signals.

Season-to-season differences come from the mix of circulating influenza subtypes, residual population immunity from prior waves, vaccine match, and the behaviour of SARS-CoV-2 variants. RSV also contributes, especially in years where earlier low-circulation periods have left younger children more susceptible. NIZP PZH's bulletins and ECDC's ERVISS both contextualise each season against prior reference periods, which is why the qualitative tiering matters more than absolute counts.