With the increase in seasonal infections, the flu is affecting a large segment of the population, often with fever that rises and falls for days. What to know about the K variant, when to worry and how to treat yourself correctly
Holidays ruined for millions of Italians: the flu epidemic is hitting our country hard, but not only. Throughout Europe the number of cases is growing exponentially, so much so that in the United Kingdom this year’s epidemic has been nicknamed “Flunami” from influence (flu in English) e tsunami. As was already clear since Australia was hit heavily, in recent months (which in the southern hemisphere were the winter ones) the 2025 flu is of a higher intensity than the average of recent years, and epidemiological data show that the majority of cases are attributable to the H3N2 influenza A viruswith the K subvariant now dominant in Europe and responsible for more than 80-90% of confirmed infections.
In our country, they occurred in the week between 15 and 21 December 950 thousand new cases, and from the beginning of the surveillance phase we are already at almost 6 million Italians affected. Not everything we think of as the flu, however, actually is. Amcli Ets, the Association of Italian clinical microbiologists explains in fact that “Overall, influenza viruses are responsible for approximately a quarter of the respiratory infections detected, with a prevalence of the A/H3N2 strain present in the seasonal vaccine, while the remaining cases are mainly attributable to rhinovirus, adenovirus and parainfluenza viruses, in addition to Covid-19 Sars-CoV-2. Faced with the simultaneous circulation of multiple viral agents, clinical diagnosis based solely on symptoms does not allow the agent to be identified with certainty responsible for the infection”. To be sure of treating the disease correctly, it would always be advisable to carry out a swab, also because Covid-19 remains much more at risk of even serious complications and therefore identifying it is still important also for the purpose of avoiding contagion to the elderly and frail.
Characteristics of H3N2
The A/H3N2 virus it is a flu strain that has been known for decades and is among the main causes of seasonal waves in the world; tends to mutate more rapidly than other subtypeswhich may favor wider spread and more pronounced symptoms in some segments of the population. There K subvariant of H3N2, which emerged in recent months in the southern hemisphere, then also gained ground in the northern hemisphere, giving the current flu season an early trend and with very high numbers of cases. The typical clinical picture associated with this flu season is the classic “strong flu” one: the fever rises rapidlyoften above 38 °C, but can fluctuate throughout the daywith evening peaks and morning drops that can last a few days. This dynamic is an expression of the immune response to the viral infection and does not necessarily indicate a complication. Intense muscle paindry cough, sore throat, chills and a profound feeling of tiredness complete the picture, which in children can be accompanied by gastrointestinal disorders such as vomiting or diarrhea. This variant of the flu, however, in addition to the classic trend, can also present a longer and fluctuating coursewith a resumption of fever after an initial respite, then a “double peak” after a phase of improvementa longer duration (up to 9 days) and persistent symptoms such as fatigue and pain: a typical trend of an immunoevasive flu.
Use of antibiotics? Only on medical prescription
The Antibiotics are useless against the flunot even when supported by the stock A/H3N2 or its variant K, because it is a viral infection. Resorting to antibiotics makes sense only in very specific circumstanceswhen the flu infection yes superimposes a bacterial complication ascertained or strongly suspected by the doctor. In practice, antibiotics are used only if the doctor thinks it is no longer just the flu. It happens especially when, after a few days of illness, the course improves it gets significantly worse. Another scenario is that of high and persistent fever beyond 4–5 daysespecially if associated with productive cough with thick or foul-smelling sputum, chest pain, difficulty breathing or marked worsening of general conditions. These are situations that can indicate a bacterial pneumoniaone of the most feared complications of the flu. Antibiotics may also be needed in case of ear infections, sinusitis or bacterial bronchitisbut only when the symptoms are clearly indicative and cannot be explained by the virus alone. In particular, persistent purulent secretions, intense localized pain or important systemic signs point the doctor towards a bacterial cause. What should be avoided is “preventive” or “for safety” use. Taking antibiotics during the flu does not speed up healingdoes not reduce viral fever and does not prevent complications. On the contrary, it exposes you to unnecessary side effects and contributes to the global problem ofantibiotic resistancemaking these drugs less effective when they are really needed. There fever it can be treated with antipyretic drugs when it exceeds a threshold that causes significant discomfort. The goal is not to “reset” it, but to make it tolerable. Fever is part of the immune response and continually lowering it for no reason does not speed up recovery. What is fundamental, however, is the hydration. With fever you lose a lot of fluids, even without realizing it. Regularly drinking water, herbal teas or broths helps avoid dehydration, drop in blood pressure and worsening of the feeling of weakness. Even when your appetite is low, small, light meals help support your body.
Avoid going to the emergency room
The emergency room is not the place to manage uncomplicated flu. Influenza, even with high fever, marked pain and severe fatigue, is in the vast majority of cases a self-limiting disease. In the absence of signs of severity, the approach remains at home or entrusted to general practitioner, who knows the patient’s clinical history and is able to evaluate the evolution over time. In the emergency room, however, you are evaluated to exclude emergencies, not to follow the course of a common viral disease. Then there is the theme of waiting times. During peak flu periods, emergency rooms are often overcrowded. Those arriving for fever, cough and flu-like pain risk waiting many hours without obtaining any concrete benefit, other than confirmation of what is already suspected: influenza in the acute phase. Another crucial aspect is the risk of contagion. The emergency room brings together frail people, the elderly, immunosuppressed people, patients with cardiovascular or oncological pathologies. Going there with the flu means increasing the risk of transmitting the virus to those who could develop serious complications. It is one of the reasons why, during flu waves, we insist on the importance of staying at home if there is no real need for urgent treatment.
The 2025-2026 flu season, dominated by A/H3N2 virus and its K subvariantalso confirms every year the importance of epidemiological surveillance and good prevention practicesincluding vaccination, especially for those belonging to risk groups. Although virus mutations can partially reduce the effectiveness of vaccines, protection against severe forms remains significant and can limit hospitalizations and complications.
