Influenza Season Takes a Darker Turn: What's Behind the 'Super Flu' Outbreak?
The US and UK are facing an unprecedented flu season, with severe outbreaks reported in both countries. The Centers for Disease Control and Prevention (CDC) has labeled this year's influenza season as the most severe since 2017-18, while in the UK, the outbreak began earlier than ever before. The cause of this unusual surge is a new variant of the H3N2 strain, known as subclade K.
Genetic analysis by the UK Health Security Agency has revealed that 87% of H3N2 viruses detected since late August are subclade K. This strain has undergone significant mutations in its hemagglutinin protein, making it antigenically distinct from previous variants used in vaccines. As a result, people infected with this new strain may be more susceptible to illness.
The term "super flu" is often used to describe this strain, but it's not an official medical term. The reality is that the H3N2 strain has already caused severe illness in vulnerable populations like the elderly and young children, and subclade K hasn't significantly increased its deadliness. The outbreak does, however, pose a significant threat to public health due to the reduced immunity of the population.
One reason for this early outbreak might be the decline in immunity resulting from countermeasures against COVID-19. The influenza epidemic was largely suppressed during the three years of the pandemic, which led to a decrease in physical strength and possibly weakened immune systems. This is reflected in Japan's data, where 22 out of 23 H3 virus strains collected between September and November were subclade K.
The current vaccine for the 2025-26 season is based on the conventional J2 lineage (subclade), which differs from subclade K in terms of antigenicity. Early data suggests that vaccinated individuals are still relatively safe, with 70-75% of vaccinated children and 30-40% of adults not requiring hospitalization or emergency room visits after infection.
To combat this outbreak, basic prevention measures remain crucial: vaccination is recommended for vulnerable populations like the elderly, pregnant women, and those with underlying medical conditions. Thorough hand washing, mask-wearing in crowded areas, maintaining proper ventilation, and humidity levels can also help suppress viral activity.
Symptoms of influenza should be taken seriously but not panic-provoked. People are advised to wait at least 12 hours after fever onset before visiting a healthcare facility and refrain from going out for five days after symptoms appear or when the fever has subsided (three days for children). Rest, hydration, and anti-influenza medication can also provide relief.
The key to managing this outbreak lies in combining vaccination with proper infection control measures. By staying informed and taking responsible actions based on scientific evidence, society as a whole can protect its health during this unprecedented season.
The US and UK are facing an unprecedented flu season, with severe outbreaks reported in both countries. The Centers for Disease Control and Prevention (CDC) has labeled this year's influenza season as the most severe since 2017-18, while in the UK, the outbreak began earlier than ever before. The cause of this unusual surge is a new variant of the H3N2 strain, known as subclade K.
Genetic analysis by the UK Health Security Agency has revealed that 87% of H3N2 viruses detected since late August are subclade K. This strain has undergone significant mutations in its hemagglutinin protein, making it antigenically distinct from previous variants used in vaccines. As a result, people infected with this new strain may be more susceptible to illness.
The term "super flu" is often used to describe this strain, but it's not an official medical term. The reality is that the H3N2 strain has already caused severe illness in vulnerable populations like the elderly and young children, and subclade K hasn't significantly increased its deadliness. The outbreak does, however, pose a significant threat to public health due to the reduced immunity of the population.
One reason for this early outbreak might be the decline in immunity resulting from countermeasures against COVID-19. The influenza epidemic was largely suppressed during the three years of the pandemic, which led to a decrease in physical strength and possibly weakened immune systems. This is reflected in Japan's data, where 22 out of 23 H3 virus strains collected between September and November were subclade K.
The current vaccine for the 2025-26 season is based on the conventional J2 lineage (subclade), which differs from subclade K in terms of antigenicity. Early data suggests that vaccinated individuals are still relatively safe, with 70-75% of vaccinated children and 30-40% of adults not requiring hospitalization or emergency room visits after infection.
To combat this outbreak, basic prevention measures remain crucial: vaccination is recommended for vulnerable populations like the elderly, pregnant women, and those with underlying medical conditions. Thorough hand washing, mask-wearing in crowded areas, maintaining proper ventilation, and humidity levels can also help suppress viral activity.
Symptoms of influenza should be taken seriously but not panic-provoked. People are advised to wait at least 12 hours after fever onset before visiting a healthcare facility and refrain from going out for five days after symptoms appear or when the fever has subsided (three days for children). Rest, hydration, and anti-influenza medication can also provide relief.
The key to managing this outbreak lies in combining vaccination with proper infection control measures. By staying informed and taking responsible actions based on scientific evidence, society as a whole can protect its health during this unprecedented season.
! 87% of H3N2 viruses detected are subclade K? That's insane! 
The fact that the vaccine is based on the conventional J2 lineage, which differs from subclade K in terms of antigenicity, is a major concern. 
I'm surprised it didn't increase deadliness 
. And what's with the decline in immunity due to COVID-19 countermeasures? 
That makes total sense now. Interesting how Japan's data matches this trend 
. Vaccination and proper infection control measures are key, but we need to stay informed and take responsibility 
.