Mexico confirms first case of so called 'super flu; variant

Dec. 15 (UPI) -- Mexico has confirmed its first case of influenza A(H3N2) subclade K, a variant commonly referred to as the "super flu," health authorities said, as the Northern Hemisphere faces an unusually early and intense flu season.

The infection was detected by the National Institute of Respiratory Diseases and confirmed by the Health Ministry, which said the patient recovered without complications and did not require hospitalization.

Influenza A(H3N2) is a respiratory infection caused by a subtype of the influenza A virus known for mutating rapidly, a characteristic that can contribute to outbreaks and complicates long-term immunity.

Symptoms are similar to those of other seasonal flu strains and include fever, headache, muscle pain, cough, nasal congestion, sore throat and general malaise.

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influenza A(H3N2) subclade K has been detected and is actively circulating in the United States. Recent surveillance reports by the Centers for Disease Control and Prevention confirm that since late September 2025, the majority of influenza A viruses identified in the U.S. belong to this subclade, making it the dominant strain this season.

In some cases, the infection can lead to severe complications and even death from respiratory problems, particularly among vulnerable groups, Infobae reported.

Mexican health authorities said the detection does not represent a public health emergency, but confirms the variant is circulating in the country, reinforcing the need to intensify epidemiological surveillance, monitoring of respiratory cases and preventive measures.

Officials said the clinical features of influenza A(H3N2) subclade K do not differ from seasonal influenza and that treatment and prevention guidelines remain unchanged.

Influenza cases typically rise each winter. In 2025, however, several countries reported the season began weeks earlier than expected.

Japan first reported a surge in influenza cases before the official start of the season. Several

European countries, particularly Spain, later reported unusual increases. More recently, the United Kingdom has seen a rise in cases and authorities there have renewed recommendations to wear face masks in public spaces.

The spread has coincided with the onset of winter and a sustained rise in seasonal influenza cases, placing pressure on health systems due to higher numbers of consultations and hospitalizations, especially among older adults, without evidence of greater severity or lethality compared with other variants.

Health authorities stress the so-called "super flu" is not a new virus or a more lethal strain, but a genetic variation within H3N2. Its significance lies in its potential to spread and its impact on health services, particularly among older adults and people with chronic conditions.

In Peru, the Health Ministry declared a nationwide epidemiological alert over the risk of the entry and spread of diseases from abroad, including influenza A(H3N2) subclade K and measles.

The alert does not mean cases of subclade K have been confirmed in Peru. It aims to strengthen surveillance, diagnostic capacity, immunization, public communication and health system response.

The measure comes amid increased international travel, high domestic mobility and year-end holiday gatherings.

The World Health Organization continues to recommend vaccination for the most vulnerable groups, saying seasonal protection can prevent severe illness and hospitalizations.