The Annual Report of the National Program for Surveillance of Influenza and Other Respiratory Viruses (Pnvg) for the 2024/2025 season from the Dr. Ricardo Jorge National Health Institute (Insa) reveals excess mortality recorded between the week of December 23 to December 29 (52) and the week of January 20 to January 26, 2025 (04).
This period coincided with the flu epidemic and a phase of extreme temperatures, as noted in the report presented at the 11th Meeting of Epidemiological Surveillance of Influenza and Other Respiratory Viruses in Portugal.
The report also notes that several other European countries experienced excess mortality from all causes, possibly attributed to the influenza epidemic and extreme temperatures.
The document describes the clinical and laboratory characterization of influenza and respiratory virus activity detected during the 2024/2025 season, which was characterized as a “long epidemic period,” with heightened flu activity between December 2024 and March 2025, with the highest number of cases identified between January 6 and January 26.
In Sentinel Networks, most reported cases were over 15 years old, with the highest percentage of flu cases found in the 5 to 14 age group, decreasing with age up to 80 years.
An increase in the proportion of COVID-19 cases was observed with age, reaching its highest (3.6%) in the 65 to 79 age group.
The genetic characterization of SARS-CoV-2 viruses detected in the Sentinel Networks of the Pnvg showed the diversity and circulation of SARS-CoV-2 lineages in Portugal, with the majority of viruses identified belonging to the BA.2.86 lineage of the Omicron variant.
The Portuguese Laboratory Network for the Diagnosis of Influenza and Other Respiratory Viruses reported 138,253 cases of respiratory infection, for which laboratory diagnosis was performed.
The influenza virus was detected in 20,140 of these cases, with 62.3% (12,543) of the cases showing the ‘influenza’ virus.
Respiratory viruses were detected in a higher proportion of cases in children under 15 and adults aged 65 and older.
Hospitals reported 125 flu cases requiring intensive care unit (ICU) admission. Most patients admitted were 55 years or older and were male.
It was found that 86.4% of patients had underlying chronic disease or risk factors, with cardiovascular disease most frequently reported (33.6%), followed by obesity (25.8%) and diabetes (23.2%).
Among patients with available vaccination status information, 104 (31.7%) were vaccinated against seasonal flu, and considering those with a vaccination recommendation, 116 (34%) were immunized.
The report indicated that the 2024/2025 ICU season presented an overall profile consistent with pre-COVID seasons, suggesting a return to pre-pandemic seasonal flu epidemics.
Insa emphasizes the importance of monitoring the severity profile of influenza, as well as vaccination against seasonal flu.
The data indicate “alternating circulation of type A and B viruses, with the Victoria-lineage of type B flu dominating from November to December and type A flu from January to May.”
The report highlights that “A(H3N2) subtype viruses exhibited antigenic and genetic characteristics distinct from the vaccine strain (crucial for the forthcoming season).”
Insa also stresses that “the A(H5N1) flu virus now constitutes a threat to public health.”
