What to Know About the New ‘Subclade K’ Flu Variant

The flu season has arrived early in the UK. Cases began increasing in October, more than a month before the season began, according to epidemiologists. This wave is driven by a new variant, and although flu viruses are constantly evolving, this one has accumulated an impressive number of mutations relatively quickly.

“This one has evolved a little more quickly, with more changes than we usually see,” says Jamie Bernal Lopez, consultant epidemiologist at the UK Health Security Agency (UKHSA).

What is subclade K?

The variant is known as influenza A, subtype H3N2, subclade K – sometimes called “subclade K” for short – and it has also been detected in Japan, where public health authorities declared a flu epidemic last month.

The mutations mean the variant is a little different from the viral material included in the updated vaccines this year. In late October, Canadian scientists warned that the mutations merited close observation, including regular sequencing of the virus’s DNA and checks to see if current vaccines work.

On November 12, Bernal Lopez and colleagues at the UKHSA published preliminary results from the United Kingdom, suggesting that so far vaccination still provides significant protection against hospitalization and severe disease.

However, they note that the level of protection is closer to what they usually expect at the end of a flu season, when the effectiveness of the vaccine has declined a bit and the mismatch between the vaccine and the virus has increased.

Does this mean that the latter stages of this season will be particularly bad?

“The flu is notoriously unpredictable, so it is very difficult for us to predict what will happen,” explains Bernal Lopez. It’s possible “that we’ll have an earlier season and end sooner, but I think the fact that we’ve seen earlier activity — and the fact that we have this subclade concern — increases the risk that we’ll see a more intense flu season than usual.” »

Dr Antonia Ho, professor and consultant in infectious diseases at the University of Glasgow, adds that earlier flu seasons often mean more people get the flu. Plus, seasons caused by H3N2 flu, like this one, also tend to hit older people pretty hard, she says.

Is subclade K found in the United States?

During the government shutdown, the flu tracking website maintained by the U.S. Centers for Disease Control and Prevention was not updated. As of November 13, the latest available figures are from the last week of September, when flu activity was low.

However, the New York State Department of Health’s influenza surveillance report for the week ending November 1 showed an increase in laboratory-confirmed influenza cases, up 49% from the previous week. Flu-related hospitalizations are up 71%, with levels roughly matching last year’s levels at this point in the flu season. The data does not include detailed subtyping, so it cannot reveal whether the new variant has arrived.

How to protect yourself from the flu

The best protection against the flu, emphasizes Bernal Lopez, is to get vaccinated. Every year, the flu kills thousands of people and is particularly dangerous for young and old people. “Children are at increased risk of getting severe flu, so it’s very important that they get vaccinated themselves. But it also gives them protection.” [for] their loved ones, and in particular vulnerable or elderly parents who could be exposed,” explains Bernal López. Even with the mutations of this new variant, the vaccine remains an important tool against the disease.