What is the New K Subclade Flu Variant That is Rapidly Spreading as Flu Season Surges Across the US

A mutated version of the influenza A H3N2 virus has led to severe outbreaks across the United States – sparking concerns about the winter season ahead, according to doctors. Experts say the K Subclade variant emerged earlier this year after picking up a number of mutations, which are expected to improve the virus's ability to help escape prior immunity from vaccines. Subclade K has already spread rapidly across the world and has already gained dominance in several countries in the Northern hemisphere. For the week ending December 6, the first full week after the Thanksgiving holiday, the proportion of doctor’s visits for symptoms including fever plus a cough or sore throat rose to 3.2 per cent, according to the US Centers for Disease Control

and Prevention. The CDC says at least 14 public health jurisdictions are showing moderate to high flu activity, mostly concentrated in the Northeast, including New York City, where activity is very high; New York and New Jersey, where it’s high; and Connecticut, Massachusetts and Rhode Island, which are in the moderate category. Flu activity is also high in Louisiana and Colorado. Other states and territories showing upticks are Georgia, South Carolina, Texas, Puerto Rico, and Idaho.

What is the Subclade K flu variant?

The subclade K flu variant is an infectious form of the illness, also nicknamed the “superflu” because it is thought to be a mutated version of H3N2. According to experts, influenza H3N2 appears less frequently than other versions of flu. Doctors say the “H” and “N” refer to two proteins on the surface of the virus — haemagglutinin and neuraminidase, with the numbers simply classifying which versions of those proteins are present. There are four types of the influenza virus - A, B, C, and D – with influenza A and B causing seasonal epidemics in humans every winter, per the CDC. The subclade K H3N2 strain has seven new mutations. It was first detected in Europe in June, after scientists selected the specific strains to be included in this year's flu shot. Experts believe vaccine immunity will not recognize the subclade K H3N2 virus as well.

How does it differ from the usual variety?

octors say that with the new variant, the problem is not that the virus has suddenly become dramatically more deadly - but that the small percentage of severe cases add up, so the overall impact feels worse for individuals. This week also saw the season’s first reported death of a child from the flu in the US. The subclade K subtype is circulating earlier and faster than usual, and immunity in the population is lower than expected for this time of year.

What are the new symptoms of the Subclade K flu variant?

Even though it is a new variant, doctors say H3N2 presents as typical flu with symptoms like:

• High fever
• Severe cough
• Sore throat
• Muscle and body aches
• Fatigue and tiredness
• Gastrointestinal upset
• Breathlessness
• Chest pain
• Confusion
• Severe dehydration

According to doctors, those most at risk are older adults, young children, pregnant women, and those with underlying health conditions like immunosuppression. And while children, mostly because of how much they mix, are a major engine of transmission, parents shouldn’t panic.