Cases of the 'K' variant of the flu are at a record level NHS figures show that the H3N2 flu variant has led to a much earlier spike in flu cases this season (Image: NHS)

Flu cases have skyrocketed across the UK as a mutated strain - A(H3N2) also known as subclade K - spreads rapidly. Everything you need to know about the strain:

The H3N2 strain is the dominant strain this year. This strain made up around 90% of flu samples in the UK in November.

This sub-type of flu appears less frequently than other versions of the illness which means that populations don’t have as high a level of immunity as other variants.

H3N2 variants in general are more transmissible and mutate more easily, research suggests.

Flu cases have skyrocketed 55% in a week , NHS England reports. The number o

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