K variant of H3N2 causes record outbreak in Europe and warns Latin America of winter By Carolina Costa
3 min read
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Europe faces a record outbreak of influenza A (H3N2) driven by the K variant, with early circulation and high transmissibility. Países as well as Reino Unido, Espanha, Alemanha, França and
The variant has seven mutations in the hemagglutinin protein, which reduces the effectiveness of current vaccines to around 65%. Ainda there are no confirmed cases in América Latina, but experts project introduction from March 2026.
Current situation in the main European countries
Kingdom Unido predicts up to 8,000 hospitalizations for flu next week alone, a number not recorded since 2010. The local Agência of Segurança Sanitária has reinforced emergency services.
Spain reached a rate of 112.2 cases per 100,000 inhabitants, almost ten times higher than the same period in 2024, according to Instituto of Salud Carlos III.
Germany and França activated contingency protocols with the expansion of beds and temporary hiring of professionals.
Features of the K variant
The K lineage of the H3N2 subtype dominates 95% of the cases analyzed in Europa and América of Norte. The virus began circulating in August at Austrália, reached Europa in September and is now present in 34 countries.
The mutations make the virus more contagious and reduce the protection offered by vaccines from the 2025-2026 season. Apesar Furthermore, immunization also reduces the risk of a severe form of the disease by up to 60%.
Genomic studies show that the variant has partially escaped the immunity built up by vaccines and previous infections.
Projections for América Latina
Organization Mundial of Saúde (WHO) does not record circulation of the K variant in the region until December 11, 2025.
Experts estimate peak transmission between May and August 2026 in the southern hemisphere. The advance of the outbreak in the north serves as an indicator for local planning.
- Annual vaccination remains the main preventive measure
- Risk groups should receive the 2026 dose from March
- Pregnant women and seniors over 65 have absolute priority
- Immunosuppressed people and those with comorbidities also need to update their regimen
Measures recommended by experts
Infectious disease specialists highlight the importance of bringing vaccination campaigns forward by one month in relation to traditional calendars. Países as well as Argentina, Brasil and Chile can start applying in March to ensure coverage before the fall.
Wearing a mask in closed environments is once again recommended for people with symptoms or belonging to risk groups. Higiene frequent hand washing and ventilation of closed environments complete the basic recommendations.
Remote work for mild cases and isolation of sick people reduce community transmission, according to current British experience.
Symptoms and differential diagnosis
The main signs include sudden high fever, intense dry cough, severe muscle pain and extreme fatigue. Quadros Gastrointestinal symptoms such as diarrhea also appear more frequently than in previous seasons.
Coexistence with RSV and SARS-CoV-2 makes clinical diagnosis difficult. Testes combined for influenza, covid-19 and respiratory syncytial virus gain importance in health services.
Young children and the elderly pose a greater risk of serious respiratory complications.
Preparation of health systems
Countries in the northern hemisphere expanded hospital capacity by opening exclusive wards for respiratory diseases. Canadá and Estados Unidos have seen an increasing predominance of the K variant since October.
At América Latina, ministries of health review stocks of vaccines and antiviral medicines. The OPS guides maintenance of genomic surveillance to quickly identify entry of the new lineage.
The European experience shows that bringing forward the vaccination campaign by four to six weeks can significantly reduce pressure on intensive care units.
