Why does the K mutation of the H3N2 virus strain receive attention?

Influenza A H3N2 virus has circulated around the world for decades. In the process of continuous evolution, this strain regularly appears new small branches. The K mutation was first discovered in June in the Southern Hemisphere, quickly spreading to many countries in the Northern Hemisphere such as England, Norway, Japan and some European countries.

Flu season is coming earlier

Professor Nicola Lewis, Director of the World Influenza Center at the Francis Crick Institute (London, UK), assessed that the emergence of a new branch is normal in the evolution of influenza. He also said there is currently no signal that the K mutation is evolving in an unusual way.

However, epidemiological experts are still paying attention to the K mutation because it causes the flu season in some countries to start earlier than usual. In Norway, England, and Japan, flu season starts 4-5 weeks earlier than in previous years.

As of mid-December, the number of infections in these countries has decreased, but may flare up again at the beginning of the new year. In the US, after the Thanksgiving holiday, the number of flu cases increased rapidly with more than 2.9 million cases, 30,000 hospitalizations and 1,200 deaths recorded by the Centers for Disease Control and Prevention (CDC). Most are influenza A H3N2, in which the K mutation predominates.

In Australia, flu season usually ends in October, but this year it is unusually long. Infections related to the K mutation still appeared late in the season, indicating that the virus continued to circulate.

Ability to evade immunity

When new flu variants appear, the virus will be able to evade immunity, overcoming protection from previous infections or vaccines. But initial studies showed that the K mutation did not create a clear immune gap.

According to Professor Lewis, scientific evidence shows that the human immune system still recognizes the K mutation and current vaccines still stimulate good antibody responses. People who have been vaccinated or have had the flu still have a significant level of protection.

Vaccine effectiveness

A study published in the journal Eurosurveillance November 20, showed that the influenza vaccine was still significantly effective against the K mutation. In children and adolescents, the effectiveness reached 72-75%; In adults, the effectiveness is about 32-39%. This is similar to previous H3N2 flu seasons.

The research team emphasizes that the vaccine still helps protect the body against the K mutation. The bigger problem lies in vaccination rate. In the UK, people over 65 years old have a fairly high vaccination rate, but among young people in risk groups and healthcare workers, the rate is still low. Increasing vaccination in these groups could significantly reduce hospitalizations and pressure on the health system.

Backup method

According to the Global Vaccine Alliance (Gavi), there is no evidence that the K mutation is more dangerous than other H3N2 strains. However, people should not underestimate seasonal flu. According to the World Health Organization (WHO), each year influenza causes 3-5 million severe illnesses and 290,000-650,000 deaths due to respiratory diseases.

If the flu season is dominated by the H3N2 strain, it often causes more difficulties, especially for the elderly. This strain is associated with higher rates of hospitalization and longer hospital stays than other types of flu.

To prevent influenza and the K mutation of H3N2, in addition to vaccination, people should coordinate other disease prevention measures, including: limiting contact when showing symptoms of illness; wash your hands frequently; keep the home space airy; Wear a mask when you have symptoms or when going to crowded places. These small actions help reduce the risk of spread, especially for vulnerable people such as the elderly, young children or people with underlying health conditions.