Data on influenza strains for 2025, or more precisely, for the 2024–2025 flu season, is available thanks to RespirVirNet, the Integrated Surveillance System on respiratory viruses and influenza-like illnesses (ILI). Coordinated by the Italian National Institute of Health (ISS), surveillance procedures are both epidemiological—tracking seasonal epidemic trends—and virological, monitoring circulating respiratory viruses in a given season. It is worth noting that influenza-like illnesses refer not only to infections caused by influenza viruses but also those sustained by other respiratory viruses.
We will shortly review information on the most recent season, with some comparisons to previous years. We will then move on to prevention methods, including individual interventions and environmental sanitation measures.
Which Strains Are Predominant
Epidemiological information from ISS shows that the 2024–2025 season, for which surveillance activity has just ended, was marked by significant circulation of respiratory viruses. Data also reveals that the total number of influenza-like illness cases exceeded 16 million—the highest figure since surveillance began.
Of the over 59,000 samples examined during this period, 23% tested positive for influenza viruses. Among these pathogens, influenza A viruses accounted for 66.7%, while influenza B viruses represented 33.3%.
Within circulating influenza viruses, the A(H1N1)pdm09 subtype was predominant (53.9%), followed by A(H3N2) (46.1%). For influenza B viruses, B/Victoria lineage strains were most common.
Other respiratory viruses were also detected, though at lower percentages:
- Rhinoviruses (9.8%)
- Respiratory Syncytial Virus, RSV (8.1%)
- Metapneumoviruses (3.2%)
- Coronaviruses not classified as SARS-CoV-2 (3%)
- Adenoviruses (2.6%)
- SARS-CoV-2, the agent of COVID-19 (2.1%)
Differences Compared to Previous Years
Beyond the higher total number of cases in 2024–2025, the peak incidence was actually lower compared to the previous 2023–2024 season. Specifically, the epidemic curve of influenza-like illnesses reached 17.4 cases per 1,000 individuals at its highest point, while in 2023–2024 the peak reached 18.4 per 1,000.
The 2023–2024 season showed the highest incidence ever recorded, with a particularly strong impact on children under five. However, even in 2024–2025, a cumulative incidence of 65% was observed in the 1–4 age group.
Overall, the incidence of influenza-like illnesses in the post-pandemic era has nearly doubled compared to the last pre-pandemic season (2018–2019).
As for circulating strains, the 2023–2024 season also recorded a predominance of A(H1N1)pdm09. Similarly, all type B viruses in that season belonged to the B/Victoria lineage.
Vaccines, Prevention, and Technology
The infection risk associated with influenza viruses requires appropriate prevention measures. These concern both individuals, who take steps to protect themselves, and environments, which often need frequent sanitation interventions. The latter rely on both conventional procedures and emerging technologies.
Influenza and Individual Prevention
To protect against influenza viruses, it is advisable to follow a few but effective hygiene and behavioral rules. At the same time, participation in vaccination campaigns is essential. Although aimed at individuals, these strategies benefit the entire community.
- Hygiene and behavior: Regular handwashing, especially after coughing/sneezing or touching potentially contaminated surfaces (e.g., bus handrails). If soap and water are unavailable, alcohol-based sanitizers should be used. Coughing/sneezing into disposable tissues, keeping distance from symptomatic individuals, self-isolating if sick, and wearing disposable face masks in crowded public spaces are all recommended.
- Influenza vaccination: Vaccines remain a highly effective preventive tool. They are updated regularly and administered in autumn. Vulnerable groups—such as the elderly, pregnant women, and people with chronic illnesses—should prioritize vaccination. It is also strongly recommended for close contacts of at-risk individuals and for healthcare workers.
For the composition of vaccines for the upcoming 2025–2026 season, refer to the document published by the World Health Organization (WHO).
Environmental Sanitation
Preventing influenza and other respiratory viral diseases also requires proper sanitation of environments. This is especially relevant in enclosed or high-traffic spaces, which increase interpersonal proximity and viral concentrations in the air.
- Cleaning: The first step, involving removal of visible dirt with manual methods and detergents.
- Disinfection: The second step, aiming for broad-spectrum germicidal action.
Sanitation methods include chemical and non-chemical approaches:
- Chemical sanitation: Performed with disinfectants such as ethyl alcohol, sodium hypochlorite, quaternary ammonium salts, hydrogen peroxide, and peracetic acid. Proper use is necessary to minimize toxicity and environmental impact.
- Non-chemical sanitation: Uses physical germicidal agents such as heat, ultraviolet radiation, and electromagnetic waves. These avoid the harmful effects of chemical disinfectants, though they are not entirely risk-free.
Air Purification
Managing infection risks also requires efficient purification of indoor air. Like other respiratory viruses, influenza viruses are expelled by infected people through coughing and sneezing, spreading into the air as bioaerosols. These accumulate indoors and can potentially infect others. Maintaining clean air is therefore crucial.
- Ventilation: Natural (frequent window opening) or mechanical (Controlled Mechanical Ventilation, CMV).
- HEPA filtration: Highly effective in high-risk environments (e.g., healthcare), removing airborne viral particles.
- UV-C lamps: Widely used for their germicidal power. Many air purifiers integrate UV-C lamps, but UV-C radiation is harmful to humans and requires careful use.
- Ionization: Produces electrically charged particles that interact with airborne viruses, neutralizing them.
- Electromagnetic fields: Devices emitting oscillating electromagnetic fields can inactivate airborne viruses safely for humans and animals. For example, devices developed by e4life generate such fields, damaging viral envelopes. Unlike many chemical or physical methods, e4shield™ technology follows the “One Health” approach, safeguarding both the environment and public health.