The influenza curve continues to rise in Italy. During the past week monitored by the National Institute of Health's RespiVirNet surveillance system, approximately 695,000 individuals were confined to bed due to acute respiratory infections, representing an increase of nearly 100,000 compared to the preceding week. Since the beginning of seasonal surveillance, the total number of cases has risen to approximately 4 million.
Influenza viruses, especially the A/H3N2 strain, are progressively becoming the primary agents of infections. This is a recognized strain, although it has circulated minimally in recent years, and this season it also includes a variant that has recently arisen in the Southern Hemisphere. Between December 1 and 7, the ISS's weekly bulletin reported that the incidence of respiratory infections reached 12.4 cases per thousand patients.
As in previous weeks, children under the age of four continue to be the most affected, with an incidence three times that of the general population: 38 cases per thousand. At the regional level, Lombardy, Piedmont, Emilia-Romagna, and Sardinia have the highest infection rates. Among the viruses presently circulating, the proportion of illnesses attributable to influenza is increasing, now representing approximately one-quarter of all cases. Among these, the A/H3N2 virus is currently dominant, accounting for around half of influenza cases. A novel variant of this subtype, identified as the K strain, has proliferated swiftly in recent months and has been associated with an extension of the influenza season in the Southern Hemisphere, where infection rates have persisted at elevated levels for at least one month longer than typical, as indicated by an analysis published in the scientific journal Eurosurveillance.