The start of the flu season in Spain has been brought forward several weeks and is already leaving figures much higher than usual for this time of the year.
According to the most recent epidemiological surveillance data, respiratory viruses (especially influenza) are experiencing rapid and sustained growth, driven by the circulation of subclade K, a new variant of the A(H3N2) virus that stands out for its high transmissibility and its ability to partially evade immunity.
Variant K: why is it more contagious and what makes it different?
The virologist and professor of Microbiology at CEU San Pablo, Estanislao Nistal, explains that the current upturn is related to the expansion of subclade K, a branch of the A(H3N2) virus that includes seven mutations in the hemagglutinin. These changes allow the virus to evade some of the previous immunity (including that generated by previous vaccines) and enhance its ability to transmit.
According to the specialist, the situation observed in Spain is not an exception: countries such as Japan, which declared the epidemic in October, as well as the United Kingdom and Canada, have already recorded significant increases.
Nistal warns that the flu season in Spain could be more intense than in recent years, especially if vaccination levels remain low. It also anticipates that the epidemic peak will arrive earlier than usual, which will require reinforced surveillance and health response.
Most common symptoms: high fever, cough and general malaise.
The symptoms of this variant are similar to those of seasonal influenza, although experts point out a greater tendency to present a high fever, above 38°C. Among the most common signs are:
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Muscle and joint pain
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Nasal congestion and sneezing
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Persistent cough
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Marked fatigue
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Chills
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General malaise
Pharmacist Joaquín López reminds us that over-the-counter medications are available to control the symptoms from the first hours, in order to avoid complications. Among them:
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Paracetamol: lowers fever and reduces pain
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Dextromethorphan: alleviates dry coughs
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Pseudoephedrine: helps to relieve congestion
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Caffeine: fights decay
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Chlorphenamine: reduces mucus and sneezing
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Vitamin C: contributes to tissue repair.
Risk of health saturation? What experts say
Hospitals and health centers are closely monitoring the evolution of infections: the K variant, due to its high transmissibility, could generate a higher volume of cases than expected, which would imply more consultations, hospitalizations and pressure on care, especially in the elderly and patients with chronic pathologies.
Nistal stresses that, in addition to vaccination and the usual hygienic measures, it will be key to avoid excessive use of emergency services. He recommends that mild cases should be treated at home or through primary care, reserving hospital services for serious situations.
A less effective vaccine, but still essential
The vaccine designed for the 2025-2026 season was developed before the K variant became dominant. This has led to an antigenic mismatch, which diminishes its ability to prevent infection. Even so, specialists insist that vaccination remains the essential tool to reduce severe cases, hospitalizations and complications.
Experts recommend consulting a health professional for any severe or persistent respiratory symptoms, especially in vulnerable people.
