'Super Flu' Subclade K Variant Shocks the World, Here's an Expert Explanation about the Danger

Illustration of a woman experiencing flu (Photo: Freepik/benzoix)

JAKARTA - Lately, the world has been abuzz with the emergence of a new variant of the H3N2 influenza virus called subclade K. This variant is reported to have become the dominant form of flu in several countries, including the UK, Japan, and parts of Europe.

Subclade K has a number of mutations compared to the strains used in this year's flu vaccine. In addition, this variant appears at the same time as the flu season which is earlier than usual in some countries, so the media calls it a 'superflu'.

"It is true that this new H3 subclade is classified as novel, but flu is always evolving," said Professor Nicola Lewis, Director of the World Influenza Centre at the Francis Crick Institute, London, England, quoted from the Gavi website.

"Our job as scientists is to monitor this evolution. Currently, there is no signal indicating that something is very unusual in the way this virus evolves," he continued.

Although subclade K is genetically distinct from other H3N2 and other influenza viruses currently circulating, it is still closely related to seasonal flu viruses that many people are already familiar with.

In Europe, the subclade K was first detected in Norway, then England, where the flu season started 4-5 weeks earlier than usual. Lewis emphasized that although the early season has not been seen since before the COVID-19 pandemic, this is not unprecedented.

"Flu is unpredictable and can peak again at the beginning of the year. So we encourage people to continue to take wise steps during the holiday period to help stop the spread," said Dr Alex Allen, an Epidemiologist at the UK Health Security Agency.

In some other EU countries, an increase in new flu cases is just beginning to be seen now, and the H1 type influenza virus is also circulating.

In the US, influenza cases increase after holidays and school openings, mostly due to the H3N2 subclade K. In Australia, the flu season which is usually May-October has also been extended due to this variant.

One of the main concerns with the new variant is its ability to bypass immunity from previous infections or vaccines. However, early studies show that this has not happened.

"The results show that there is no clear signal of an immune gap that this virus takes advantage of," said Lewis.

This means that the existing body defense system still provides protection, and vaccinated people still produce a good antibody response to circulating influenza viruses, including the K subclade.

The initial estimate published in Eurosurveillance suggests that current flu vaccines are still effective against severe infections due to the H3N2 subclade K.

- Children and adolescents: 72-75% effective

- Adults: 32–39% effective

Professor Antonia Ho of the University of Glasgow emphasized that the main challenge at present is the coverage of vaccination. In the UK, although the elderly are vaccinated quite well, the young adult and health care workers are still low, although increasing vaccination in this group can reduce spread, hospitalization, and pressure on health services.

"Superflu is not a scientific term, and based on current evidence, there is no indication that the K subclade is more dangerous than other H3N2s that are circulating," said Lewis.

However, calling it a common cold is also not appropriate. Seasonal flu still causes 3-5 million cases of severe illness and 290 thousand - 650 thousand respiratory deaths every year.

H3N2 is especially risky for the elderly because it tends to cause more severe illness and longer hospitalization. Dr. Allen added simple prevention measures.

"If you experience flu or COVID-19 symptoms, including high fever, cough, and fatigue, avoid contact with others, especially those who are vulnerable. Wash your hands regularly, make sure the room is well ventilated, and consider wearing a mask if you need to leave the house," said Dr. Allen.