NHS has now issued a "flu jab SOS" as fears grow that the flu cases will add up to a brutal winter. While it is every winter that the flu strikes, this year, there is something different. A seasonal flu usually mutates in the summer and thus evade some of our immunity, which may have kicked in early flu season before. A seasonal flu is thus a type that has a history of being more severe. All thanks to flu staying all round the year, flu experts have now said that they won't be shocked if this flu season becomes the worst flu season for a decade. Professor Nicola Lewis, the director of the World Influenza Center at the Francis Crick Institute told BBC, "We haven't seen a virus like this for a while, these dynamics are unusual. It does concern me, absolutely. I'm not panicking, but I am worried."What Is Happening To Flu Season This Year?Scientists have been able to track the evolution of influenza viruses because they mutate constantly, and thus the flu vaccines have to be updated every year to keep up. The evolution happens in a rhythm which is known as the "shift and drift". Most of the time the virus undergoes a minor change, however, every often there is also a sudden attempt for an abrupt shift as the virus keeps mutating. Prof Derek Smith, who heads the Centre for Pathogen Evolution at the University of Cambridge, says seven mutations in a strain of the H3N2 seasonal flu have caused a rapid rise in cases involving this altered version of the virus.Unusually, this spike happened outside the typical flu season, right in the middle of the northern hemisphere’s summer. “It will almost certainly spread worldwide, and quickly,” says Prof Smith. By September, once schools reopened and temperatures began to fall, cases started rising again.Experts are still studying the exact impact of the mutations, but they likely help the virus slip past some of the immunity people have developed from past infections and vaccines. This makes it easier for the virus to infect and spread, which is why flu season has arrived early in the UK and countries like Japan.If the virus spreads more easily, it doesn’t need to wait for cold winter conditions, when people stay indoors with closed windows, to trigger flu season. “We’re already far ahead,” says Prof Lewis. “This is likely to be a strong flu season.”Using R numbers as a guide, the new mutated strain appears to have an advantage. Seasonal flu normally has an R value of about 1.2, but this year’s early estimates put it closer to 1.4. That means if 100 people were infected, they would typically spread it to 120 others, but this year that number could be around 140.Could This Be The Worst Flu Season?Professor Christophe Fraser, from the Pandemic Sciences Institute at the University of Oxford told BBC, "It's highly likely it's going to be a bad flu season and it's going to happen quite soon, we're already well into it. There are indicators that this could be worse than some of the flu seasons we've seen in the last 10 years."In a normal flu season, about one in five people get infected, but that number could be higher this year, he warns. Still, there’s a lot of uncertainty around these predictions.Many look to Australia for hints, since it saw its worst flu season on record, although it was dealing with a different H3N2 strain than the one spreading now.Right now, the virus is circulating rapidly among children, especially in schools where germs spread easily. But the immunity of a 10-year-old is very different from that of an older adult, who has lived through many more flu seasons and carries different immune memory.Because of this, experts will be watching closely as infections begin to move into older age groups in the coming weeks.
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