With the arrival of autumn we start talking about the “Australian flu” again. It is the name by which the seasonal flu associated in particular with the A/H3N2 virus is commonly indicated, carefully observed because in the southern hemisphere the flu season arrives several months before ours.
At the end of September it is still too early to establish how intense the wave will be in Italy, but some useful elements are already there. In fact, influenza viruses continue to evolve and for this reason their circulation is monitored throughout the year, not just in the colder months.
The World Health Organization has already identified the strains to be used as a reference for vaccines intended for the northern hemisphere in the 2026-2027 season. The trivalent formulation includes viruses belonging to the A(H1N1)pdm09 and A(H3N2) subtypes, together with a virus belonging to the B/Victoria lineage. The composition is updated periodically precisely because influenza viruses change over time and the objective is to bring the vaccine as close as possible to the strains destined to circulate.
However, this does not mean that we can already predict which of the different viruses will be dominant in Italy or how strong the next epidemic will be. The data coming from the countries of the southern hemisphere, where winter arrives earlier, are carefully observed by epidemiologists, but do not constitute an early snapshot of the European winter. Climate, population immunity, vaccination coverage and virus characteristics can significantly change the trend from one region of the world to another.
There is not only “the flu virus”
When we talk about seasonal flu we are actually grouping different viruses together. Among those monitored by WHO for the coming European winter are A(H1N1)pdm09 and A(H3N2), as well as the B/Victoria lineage. The old B/Yamagata lineage, however, is no longer considered necessary in the composition of trivalent vaccines: no viruses belonging to this lineage have been documented in natural circulation since March 2020.
Updating vaccines is therefore not a bureaucratic detail. Influenza viruses continually accumulate genetic and antigenic modifications and the immunity developed in previous years does not automatically guarantee sufficient protection against those that will circulate in the following season.
To really understand what will happen in Italy we will have to wait for the start of the new surveillance. In fact, the Istituto Superiore di Sanità monitors not only influenza, but all acute respiratory infections through RespiVirNet. Since the 2025-2026 season, Italian surveillance has explicitly broadened its focus precisely because influenza, SARS-CoV-2, respiratory syncytial virus and numerous other pathogens can circulate at the same time and produce very similar symptoms.
Influenza, Covid and RSV can overlap
The difficulty in the next few months will therefore be to distinguish diseases which, especially in the first few days, can be very similar.
SARS-CoV-2 continues to circulate throughout the year and does not necessarily follow the same timetable as the flu. The ECDC also underlines that Covid has not simply transformed into an exclusively winter virus and that peaks of different respiratory viruses can also appear outside their traditional seasonality.
Then there is the respiratory syncytial virus, or RSV, which is particularly important in very young children but also potentially serious in the elderly and in people with certain chronic diseases. In most adults it causes symptoms similar to those of a common cold, while in vulnerable subjects it can affect the respiratory tract more deeply and can cause pneumonia or aggravate pre-existing heart and lung diseases.
It is precisely this overlap that makes trying to identify the virus solely on the basis of a single symptom unhelpful.
What the flu really looks like
One of the most typical characteristics of the flu is its rather rapid onset. A person may feel relatively well in the morning and within a few hours find themselves with fever, body aches, chills, headache, cough and a strong feeling of exhaustion.
Not everyone, however, necessarily develops a fever. In the elderly, in particular, the picture may be less evident, while in children respiratory symptoms may be associated with gastrointestinal disorders.
Colds, on the other hand, more often tend to appear gradually and focus more on stuffy nose, sneezing and sore throat. They are general indications, not diagnostic tools: influenza, Covid and other respiratory viruses can produce very similar pictures.
Even the loss of taste and smell, which became almost synonymous with Covid during the early stages of the pandemic, is today not sufficient alone to distinguish SARS-CoV-2 infection from other respiratory diseases. When knowing which virus is responsible changes treatment decisions or the management of a fragile patient, the doctor may consider it useful to use a test.
When symptoms should not be ignored
In most healthy people, a respiratory infection resolves without serious consequences. However, there are situations in which waiting for it to pass on its own is not a good idea.
Marked difficulty breathing, persistent chest pain or pressure, confusion, severe weakness, or sudden worsening after apparent improvement require rapid medical evaluation. Among children, very fast or difficult breathing, signs of dehydration, poor reactivity and difficulty drinking should be observed with particular attention.
In the case of RSV, especially in infants, breathing difficulty may be accompanied by poor appetite or reduced fluid intake. Also in this case the worsening of symptoms must be evaluated by a healthcare professional.
Who is most at risk of complications
Age remains one of the main risk factors, but it is not the only one. Older adults, very young children, pregnant women, and people with certain chronic conditions or compromised immune systems are more likely to develop complications from the flu.
For the 2026-2027 season, the Ministry of Health recommends influenza vaccination, particularly for categories considered most exposed to the consequences of the disease. These include people aged 60 and over, children between 6 months and 6 years old, pregnant women, healthcare workers and people with certain underlying health conditions. Compared to some indications still reported online, therefore, the Italian reference is not simply that of the over 65s.
The vaccine can be administered from six months of age and remains one of the main tools for reducing the risk of influenza and especially its complications in vulnerable people.
Swab yes or no?
Not every fever accompanied by cough automatically requires a test. In many cases the doctor can orient himself based on the symptoms, the visit and the circulation of the virus at that moment.
However, testing becomes more important when identifying the virus can change clinical management, for example in people at greater risk of complications or in patients requiring hospitalization. There are also multiple tests capable of simultaneously looking for influenza, SARS-CoV-2 and RSV.
If a complication such as pneumonia is suspected, your doctor may instead consider additional tests, such as blood tests or a chest x-ray. There is therefore no test package valid for everyone with flu: it depends on age, general conditions and the evolution of symptoms.
Prevention doesn’t start with supplements
With the arrival of autumn, products that promise to “strengthen the immune system” also return promptly. The reality is less spectacular. There is no food, supplement or natural remedy capable of creating a barrier against respiratory viruses.
The more concrete measures are much more ordinary: getting vaccinated when recommended, avoiding exposing other people when you are sick, washing your hands, improving air exchange in closed environments and evaluating the use of a mask in situations where the risk of transmission is greater. Reducing contact with vulnerable people when you have a fever, cough or other respiratory symptoms can also make a real difference.
Getting enough sleep, doing physical activity, following a varied diet and not smoking are naturally important for general health, but it would be wrong to present them as alternatives to vaccination or as a guarantee of not getting sick.
