UK flu season arrives early started growing in Octobermore than a month earlier than epidemiologists typically expect the season to start. Driving the surge is a new variant, and while flu viruses are constantly evolving, this one has amassed an impressive number of mutations relatively quickly.
“This situation has evolved a little faster, with more changes than we usually see,” says Jamie Bernal Lopez, consultant epidemiologist at the UK Health Security Agency (UKHSA).
What is subclade K?
This variant is known as H3N2 influenza A subtype 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 slightly different from the viral material included in this year's updated vaccines. At the end of October, Canadian scientists warned that mutations require careful monitoringincluding routine DNA sequencing of the virus and testing the effectiveness of existing vaccines.
November 12 Bernal Lopez and his colleagues from UKHSA. published preliminary results from the UK, suggesting that vaccination so far still provides significant protection against hospitalization and severe disease.
However, they note that the level of protection is closer to what they typically expect to see at the end of the flu season, when vaccine effectiveness has decreased slightly and the mismatch between the vaccine and the virus has increased.
Does this mean that the later stages of this season will be particularly bad?
“Flu is notoriously unpredictable, so it’s very difficult for us to predict what will happen,” says Bernal Lopez. It's possible “that we have an earlier season and that it will end earlier, but I think the fact that we've seen earlier activity—and the fact that we have this worrisome subclade—increases the likelihood that we'll see a more intense flu season than normal.”
Dr Antonia Ho, professor and consultant in infectious diseases at the University of Glasgow, adds that an earlier flu season often means more people get the flu. What's more, she said, H3N2 flu seasons like this one also tend to hit older people very hard.
Is Subclade K located in the USA?
During the government shutdown, a flu tracking site is maintained by the U.S. Centers for Disease Control and Prevention. has not been updated. As of November 13, the latest data available is from the last week of September, when influenza activity was low.
However, the New York State Department of Health influenza surveillance report The week ending November 1 saw an increase in laboratory-confirmed influenza cases, up 49% from the previous week. Flu hospitalizations were up 71%, roughly the same as last year at this point in the flu season. The data does not include detailed subtype information, so it cannot determine whether a new variant has emerged.
How to protect yourself from the flu
The best protection against the flu, Bernal Lopez emphasizes, is vaccination. Thousands of people die from the flu every year, and it is especially dangerous for young and old people. “Children are at increased risk of severe illness from influenza, so it is important that they get vaccinated themselves. But it also provides protection.” [for] their relatives and in particular any vulnerable relatives or elderly relatives who may be exposed,” says Bernal Lopez. Even with the mutations of this new variant, the vaccine is still an important tool against this disease.
The flu vaccine can take up to two weeks to work, so the sooner you get it, the better.
“This remains our best tool to protect each other,” Ho says.
