As has long been known, seasonal viruses strike more intensely during the colder months , as people spend more time indoors. At the same time, frequent heating systems and often limited air exchange coexist : conditions that favor the spread of viruses through the air. Protecting schools, offices, nursing homes, and healthcare facilities requires a combination of hygiene, vaccination, and active management of indoor air quality .
What are the main seasonal viruses?
Respiratory viruses circulating during the cold season belong to well-defined typologies , despite the changes in recent years related to the pandemic . Below is a brief examination of the viruses in question.
Influenza: strains, seasonality and peaks
Seasonal influenza , caused by type A and B viruses that are constantly evolving in antigenic terms, follows a typical autumn-winter pattern in Italy and Europe , with the epidemic peak usually concentrated between December and February. Surveillance activities are conducted at the European level by the ECDC and in Italy by the ISS’s integrated system RespiVirNet , an evolution of the previous InfluNet . Continuous monitoring allows us to identify the predominant strains, evaluate the progress of the epidemic, and periodically update the composition of seasonal vaccines.
Respiratory syncytial virus (RSV) and rhinovirus
virus (RSV) causes flu-like symptoms in healthy adults, but can be associated with more complex syndromes in immunocompromised individuals . Its circulation peaks in Italy between January and February, with an epidemic period typically extending from October to March. Rhinoviruses , on the other hand, predominantly cause the common cold , contributing significantly to the burden of seasonal respiratory illnesses, especially in vulnerable populations.
Co-circulation with SARS-CoV-2
For some seasons, influenza, RSV and SARS-CoV-2 They co-circulate in the same months : a phenomenon that the ECDC and WHO monitor through integrated respiratory virus surveillance platforms (such as ERVISS at the European level ). This overlap, among other things, increases the overall pressure on high-traffic indoor environments, from hospitals to schools.
Why seasonal viruses strike more in winter
The winter incidence of respiratory infections is certainly no coincidence. Certain environmental and behavioral factors , in fact, favor viral transmission and contagion . Let’s see what they are.
Closed spaces, heating and poor air exchange
In winter, people spend more time indoors , often avoiding opening windows. This promotes thermal comfort but reduces natural air exchange , facilitating the accumulation of potentially infectious aerosols in classrooms, offices, public transport, and waiting rooms.
Humidity and virus survival in aerosols
Heating systems, among other things, tend to lower the relative humidity of indoor air . Several studies indicate that intermediate or very low humidity conditions may favor the greater persistence of some respiratory viruses dispersed in bioaerosols , compared to higher humidity levels.
Environments most at risk and categories to be protected
Seasonal infectious risks find fertile ground in educational and, very often, professional settings, where social gatherings are the norm . But that’s not all. Healthcare facilities also suffer the consequences of high indoor attendance, with significant risks for vulnerable individuals.
Schools, offices, nursing homes and healthcare facilities
Classrooms, university environments, and open -plan offices , as well as nursing homes, hospitals, and multi-specialty medical centers, are the settings where the transmission of seasonal viruses is most likely and where prevention measures have the greatest potential impact . In these settings, the simultaneous presence of numerous people, combined with the sharing of spaces and surfaces, makes it extremely important to address air quality , in addition to traditional hygiene and sanitation measures.
Fragile subjects: elderly and immunocompromised
The elderly and immunocompromised are among the groups most vulnerable to complications from seasonal viruses , and public health recommendations focus more closely on these groups each year. Reducing the circulation of viruses in shared environments represents a form of indirect protection , especially for those at greater risk of developing severe forms of the infectious disease.
Protection strategies for indoor environments
Limiting the spread of seasonal viruses in confined spaces requires an integrated approach , capable of combining individual behavioral measures and targeted interventions in shared spaces.
Hygiene, vaccination and individual behaviour
Basic measures remain essential: hand hygiene, respiratory etiquette (covering your mouth and nose when coughing or sneezing), self-isolation if symptoms develop , and, for those in the recommended population, seasonal influenza vaccination , which remains the primary prevention tool with the most scientific support. Accurate information on appropriate behaviors also contributes to increasing the effectiveness of prevention strategies through increased awareness.
Air quality management: ventilation, filtration and inactivation
Alongside individual measures, indoor air quality management represents a complementary and continuous level of intervention: ventilation to dilute viral particles in bioaerosols , HEPA filtration to retain airborne particulate matter , and, as an additional layer, viral inactivation technologies Air : Designed, like e4shield TM , to act on the residual viral load in the occupied environment. The integration of these solutions allows for constant intervention even when natural air exchange is insufficient.
An active and continuous solution throughout the season
During the cold season, active and continuous management of indoor air quality allows for maintaining a constant level of protection in high-traffic areas, without relying solely on opening windows. The adoption of targeted indoor air sanitization systems is ultimately a valuable complement to traditional prevention measures, helping to create safer and healthier indoor environments during the most “critical” time of year.
FAQ — Frequently Asked Questions
- What are the most common seasonal viruses in winter?
The main ones are influenza viruses (types A and B), respiratory syncytial virus (RSV), rhinoviruses , and SARS-CoV-2, which often co-circulate in the same environments in winter, increasing the overall burden of respiratory diseases.
- Why do we get sick more in winter?
Because we spend more time indoors, with windows closed and less air exchange for thermal comfort, this favors the accumulation of potentially infectious aerosols. Furthermore, drier air due to heating can favor the longer persistence of some viruses.
- What’s the difference between the flu, the common cold, and Covid?
They are caused by different viruses (influenza viruses, rhinoviruses /other cold viruses, SARS-CoV-2), often with similar symptoms but varying severity. Colds typically cause mild upper respiratory symptoms, while influenza can cause high fever and severe muscle aches, while COVID-19 has a variable course and may also include loss of smell/taste. A definitive differential diagnosis requires specific tests.
- How to protect an office or school from seasonal viruses?
Combining hand hygiene, appropriate behavior when symptoms occur, regular ventilation of rooms, and, where possible, continuous air filtration and treatment systems, in addition to vaccination for the recommended groups.
- Does air purification help against the flu?
Yes, air quality management, through ventilation and filtration, and possibly viral inactivation technologies, can help reduce the concentration of airborne viral particles in indoor environments, as a complementary (not a replacement) measure to hygiene and vaccination.
- What is the difference between filtering and inactivating viruses in the air?
Filtering means mechanically retaining particulate matter, including viral particles, on a filter medium (e.g., HEPA); inactivating means acting directly on the viral particle to reduce its infectivity. These approaches are complementary, not alternatives.
